Absolutely right. Thinking you're going to take a Bridgeport with .015" backlash in the acme screws and comp it out with software is a fallacy. If that worked machine tools wouldn't need ground ways with scrapped Turcite, ball screws, pressure fed oiling systems. Just whack the machine together out of cold rolled, put a bunch of sensors on it, and comp the whole thing in software as it teeters along.
Take circular interpolation, the X is slowing down as it gets to the right or left side at which point the Y is going full tilt, when X hits the turn around point, what does the X do, jerk the .015 out? Even if some algorithm "eases" it out over time, you still don't have a circle!! And even if it jerks it out, it can't jerk it all out in 0 time while the Y is going full feed rate. 015" is just an exaggeration to make the point, but the same thing happens trying to comp .0015" out. It DOES sound good in the literature, tho'.
All these motion controller sellers spending all this time on Backlash Compensation when they could be spending time on real stuff.