mcpi | Minecraft : Pi Edition API Python Library

Per comments on the documentation for mcpi, it would appear that the coordinates are relative to the world spawn:

getPos, getTilePos, setPos and setTilePos all appear to be relative to the player's spawn point at least in a single player world. I am going through trying to teleport my character but the coordinates I end up on are not the world's coordinates but a coordinate relative to where my character would spawn.

This appears to hold true with the results you observed, which were that different coordinate pairs produced a common difference in the expected and actual coordinates (i.e. (0, 32, 0) (0, 98, 0); (0, 62, 0) (0, 128, 0)).

So, either fix an offset of 66 blocks into the y-axis values, or manually set the world spawn to (0, 0, 0) with /setworldspawn.