Noticed this issue through an unusual sequence of events.
We are midway through a lathe conversion, in the mean time we are using EMC with linear scales as a glorified DRO.
However we noticed that when doing a touch off (to zero the display) it was always going to a fixed offset.
It turns out that the offset is the commanded position.
Basically when you press touch off, it is setting the co-ordinate system based on the commanded position rather than the actual position, given a servo system may well have some ferror at the time the end user is touching off it seems it would be more accurate to use the actual position than the commanded position for this process.