Pressure sensitivity for the Apple Pencil is built into the Pencil, not the display. This is fairly common for pressure-sensitive drawing tools. I don't think any model of iPad has a pressure-sensitive display.
AsAccording to Wikipedia, iPhone generations 6 - X had some models with pressure-sensitive displays, but this feature has been discontinued, and was never used in iPads.
Also, as it says in the documentation that you linked to, you can use Input.touchPressureSupported to see if the device has a pressure-sensitive touchscreen.
