Yep. It's interesting that that's how range is measured, but not how movement is measured. Particularly because the designers know the base dimensions in advance and could easily subtract them in order to provide the adjusted MOV values. If you round them off for Imperial measurement purposes you get: 25mm base = lose 1" per MOV value (4-4 becomes 3-3, 6-2 becomes 5-1) 40mm base = lose 1.5" per MOV value (4-4 becomes 2.5-2.5, 6-4 becomes 4.5-2.5) 55mm base = lose 2" per MOV value (4-4 becomes 2-2, 6-4 becomes 4-2, 8-4 becomes 6-2, etc.)
^ doesn't work with Prone. I mean we do that in practice, but "measure from the same abstract point in the SIL" achieves the same outcome and is simple. Yes the measuring diagram should show rotation (90 degree corner. Trooper starts facing up, turns 90 degrees but measurement uses the same abstract point).
Prone movement being reduced to half (round down) will get pretty close in most cases because the rounding will tend to take care of the offset due to base width that isn’t being halved. It would also be possible to have a zero move, where you displace the width of the base or less, as a defined part of the movement rules. FWIW, I think the current system is fine, it could just use more diagrams showing examples.
