If it doesn’t make the scheduler do better retrievability prediction then I’m not sure Hard and Easy are doing anything beneficial here. I am only countering what you said - that it would hamper the scheduler’s performance. Is there anything else a scheduler does other than showing you the cards at the correct time (in this case, when R falls to a particular value). Also to quote you,
This is from 2020 by the way.
In any case, I saw L.M.Sherlock creating a repo called Anki button usage so he might be working on something here.
(@Expertium I think I misquoted but here you go. I wanted to reply to this)