it "works" but sometimes you have to hit it a few times to get it to actually "quantize" Using latest PT 12.8.2 r2 update.
please please please fix this, also in that discussion if you hold command in slip mode it snaps to grid. If you're like sonic the hedgehog and actually go fast in pro tools this is the most detrimental feature you've ever added
here's the link again
I use input quantize all the time for drum programming. Every time I do a flam using two alternate snare keys, they end up exactly together and I have to go back and move the flam.