EF Core mechanisms in .NET Core to handle concurrency issues

I am just starting to learn about concurrent processing in EF Core to make consistent applications and I have some questions, Microsoft documentation says the following:

using var context = new PersonContext();

// Fetch a person from database and change phone number
var person = context.People.Single(p => p.PersonId == 1);
person.PhoneNumber = "555-555-5555";

// Change the person's name in the database to simulate a concurrency conflict
context.Database.ExecuteSqlRaw(
    "UPDATE dbo.People SET FirstName = 'Jane' WHERE PersonId = 1");

var saved = false;

while (!saved)
{
    try
    {
        // Attempt to save changes to the database
        context.SaveChanges();
        saved = true;
    }
    catch (DbUpdateConcurrencyException ex)
    {
        foreach (var entry in ex.Entries)
        {
            if (entry.Entity is Person)
            {
                var proposedValues = entry.CurrentValues;
                var databaseValues = entry.GetDatabaseValues();

                foreach (var property in proposedValues.Properties)
                {
                    var proposedValue = proposedValues[property];
                    var databaseValue = databaseValues[property];

                    // TODO: decide which value should be written to database
                    // proposedValues[property] = <value to be saved>;
                }

                // Refresh original values to bypass next concurrency check
                entry.OriginalValues.SetValues(databaseValues);
            }
            else
            {
                throw new NotSupportedException(
                    "Don't know how to handle concurrency conflicts for "
                    + entry.Metadata.Name);
            }
        }
    }
}

I have this code of the WeatherService:

public WeatherForecast UpdateMeasurementsForToday()
{
     var saved = false;
     var date = DateTime.Today;
     var specified = DateTime.SpecifyKind(date, DateTimeKind.Utc);

     while (!saved)
     {
         try
         {
             var entityFromDb = _source.GetWeatherByDate(specified);
             entityFromDb.TemperatureC = Random.Shared.Next(30);
             
             _source.UpdateEntity(entityFromDb);
             saved = true;
             return entityFromDb;
         }
         catch (DbUpdateConcurrencyException ex)
         {
             foreach (var entry in ex.Entries)
             {
                 if (entry.Entity is WeatherForecast)
                 {
                     var proposedValues = entry.CurrentValues;
                     var databaseValues = entry.GetDatabaseValues();

                     if (databaseValues is null)
                         throw new ArgumentException("Сущность была удалена");
                     entry.OriginalValues.SetValues(databaseValues);
                     entry.CurrentValues.SetValues(databaseValues);
                 }
                 else
                 {
                     throw new NotSupportedException(
                         "Don't know how to handle concurrency conflicts for "
                         + entry.Metadata.Name);
                 }
             }
         }
     }

     throw new ArgumentException();
}

Code from _source repository:

public void UpdateEntity(WeatherForecast newEntity)
{
    var entityFromDb = _ctx.Forecasts.First(c => c.Id.Equals(newEntity.Id));
    entityFromDb.TemperatureC = newEntity.TemperatureC;
    entityFromDb.SummaryUpdates++;
    entityFromDb.Version = Guid.NewGuid();
    _ctx.SaveChanges();
}

And I have a question, why when we get DbConcurrencyException we do some extra steps like in Miscrosoft documentation?

Can't we just go back and ask for NEW data (I tried this way and it really didn't work properly, the loop was endlessly throwing DbConcurrencyUpdateEx, I think it's due to the fact that EF Core caches data).

Another issue is when we may need a situation where we need our proposed values and NEW values from the database to resolve a conflict, because our proposed values are based on the old ones, logically it seems as if we just need to write

entry.OriginalValues.SetValues(databaseValues);
entry.CurrentValues.SetValues(databaseValues);

and kind of suggest new values.

But in the documentation we again go through the properties in detail.

Also, probably obvious for an insider, but I genuinely don't understand why my concurrency test is unstable:

public async void UpdateWeather_Updatingsimultaneously_SummaryShouldConsiderUpdateCounters()
{
     var rep1 = new EfWeatherRepository(_ctx1);
     var rep2 = new EfWeatherRepository(efDbInitializer.Ctx);
     var weatherService1 = new WeatherService(rep1, _fakeService.Object);
     var weatherService2 = new WeatherService(rep2, _fakeService.Object);
     var createdEntity = weatherService1.MeasureTodayWeather();
     var task1 = Task.Run(() => weatherService1.UpdateMeasurementsForToday());
     var task2 = Task.Run(() => weatherService2.UpdateMeasurementsForToday());
     await Task.WhenAll(task1, task2);
     var result = rep1.GetEntityById(createdEntity.Id);
     result.SummaryUpdates.Should().Be(2);
}

I'm intercepting the conflict, updating the data and loading the weather entity into the database with the NEW data, but sometimes the test fails because the number of updates is 1 instead of 2. Class definition

public class WeatherForecast : IUnique
{
    public int Id { get; set; }
    public DateTime Date { get; set; }
    public int SummaryUpdates { get; set; }
    public int TemperatureC { get; set; }
    [NotMapped]
    public int TemperatureF => 32 + (int)(TemperatureC / 0.5556);
    [ConcurrencyCheck]
    public Guid Version { get; set; }
    public string? Summary { get; set; }
}

Sql table definition (I have only 1 table)

"forecasts" "public"    "Forecasts" "Id"    1       "NO"    "integer"
"forecasts" "public"    "Forecasts" "Date"  2       "NO"    "timestamp with time zone"
"forecasts" "public"    "Forecasts" "SummaryUpdates"    3       "NO"    "integer"
"forecasts" "public"    "Forecasts" "TemperatureC"  4       "NO"    "integer"
"forecasts" "public"    "Forecasts" "Version"   5       "NO"    "uuid"
"forecasts" "public"    "Forecasts" "Summary"   6       "YES"   "text"

I used the code from the MS documentation