Most people don't hear it over the whacking of the keys against the keybed while they're playing, and may not hear it in a mix with drums and other sounds going on. For the first few years I had a mono desktop evolver, and it was harder to hear with just one voice cycling - In the mono case I frequently just used it for parts within a 2-octave range, so it was inaudible or tolerable.
It becomes much more of an issue if you're playing the Poly and using two hands/spreading your notes across octaves.
Regarding "slop" - that's not what Dave Smith was referring to.

He was referring to the "Oscillator Slop" parameter, which doesn't affect this glitching.