Do a simple profile cut square with the same bit, depths and feed rates. Measure that. Now, with the same vectors, change the toolpath to 0,5mm depth or so so it just barely cuts the surface. If there is no bit deflection or machine deflection then the results will be identical.
I have tried this and the results are identical
I have just tried "fooling" the machine by editing the tool diameter. My 70 x 40 hole is now 70 x 40 but this only works with a single tool pocket. If I use a two tool (clearance and final) then the second, smaller bit does not remove any material apart from a very small piece in the corners