Should the rulers not be measuring from the Toolpath Zero instead of the lower-left corner?
I suspect that the intention is to keep things simple and to always show the consistent measurement for the stock area — an option to set ruler origin to match the Toolpath Zero would be nice though.
‘Consistent’ is not always the same as ‘easy to use’. If the stock is an odd size (not a nice multiple of the grid size, for example), then having the rulers mis-aligned with zero makes them very hard to use. Every time you use the ruler you end up doing the mental math to get rid of the offset, so that you can work in a sensible co-ordinate system (i.e., one based on toolpath zero). Obviously fraught with errors.
I actually think the current scheme is inconsistent with users expectations, even though it is graphically consistent.