Status of SE-0270 (Add Collection Operations on Noncontiguous Elements)

Is there any reason that SE-0270 is still previewing 3 years after its formal acceptance into the language? Maybe I overlooked something while quickly skimming the relevant review threads, but it seems to be just forgotten. If it isn't and there is actually a reason why it's not yet part of the language, maybe that should be communicated somewhere a bit more prominently.

(And no, I'm definitely not asking because of today's Advent of Code puzzle^^)


The proposal has been resurrected a couple weeks ago: [Pitch Revision #4] Add Collection Operations on Noncontiguous Elements