The PR does a great job linking to other discussions about this, including an -ideas thread from two years ago. I haven’t read through everything yet, but I notice that the first objection last time around was David Mertz pointing out that it’s not even in more-itertools, so maybe that more-itertools PR means it’s the perfect time to reopen this discussion? Or maybe it means we should wait a few months and see if people seem to be using the one in more-itertools? (And also maybe to wait for it to stabilize—there are a few bug fix commits to it after the initial merge.)