I think it’s more the opposite. Apple likely decided early on for the 10th gen to be compatible with Pencil 1 so folks with the 9th gen could upgrade if they so desired and keep their pencil. Having made that decision, since they weren’t going to use the space, they decided to move the camera.About the choice for the old Apple Pencil 1 on the new iPad 10th gen.
I think I know why Apple chose to just support Pencil 1 on the new regular iPad. My guess is that somehow they didn’t figure out yet how to combine a magnetic charging spot and the FaceTime cam at the same side.
For something like the iPad Pro, they could always keep the charger where it is and move the camera array into the screen area… iPad Dynamic iSland.