There’s very little to explain though. I screwed up by beginning my explanation of this feature request at a high level, but if you look at https://forum.inaturalist.org/t/make-needs-id-independent-of-both-research-grade-and-casual-statuses/52795/29?u=regnierda, it’s far from mind bending.
When and how things go to GBIF and what observations you retrieve using the default search filters all remain the exact same. The new elements are new search filter options and an additional indicator at the top of the observation page.
You mention taxon specialists, and it feels like most comments thus far on this thread have evidenced a perception that across the entire taxonomic tree all or most subspecies are extremely difficult to ID if you’re not an expert in that specific taxon. That’s simply not true. Sure there are plenty that are dubious, or even if valid they’re still extremely difficult to tell apart, but (1) that’s not a problem specific to subspecies, and (2) there are plenty of subspecies that are not dubious and are not extremely difficult to tell apart.
I’m a generalist that focuses on the state where I live, and I actually can’t think of any subspecies offhand that were a a huge ordeal to learn to ID (except maybe Chenopodium berlandieri bushianum). While they often require smaller details to ID, details that people may be less likely to capture (because they don’t know it’s an important detail, that is until I explain it to them when I put a species-level suggestion and a comment on their observation), I’ve found the subspecies that I’ve encountered in my area to be as generally straightforward to ID as were their parent species.
I can however think of numerous species that were (or still are) extraordinarily difficult to learn, and/or ID even once learned – Stellaria spp., Polygonum spp. (not everything is P. aviculare, not everything is even in the P. aviculare complex!), and various members of Amaranthaceae, to name a few.
I continue to disagree wholeheartedly with the notion that subspecies (or variety, or form, or whatever other infraspecific ranks are out there) are vastly different than any other rank or that they should be treated any differently than species as far as iNaturalist’s “help me find stuff to ID” design goes.
The problem is that iNat doesn’t actually have a “help me find stuff to ID” mechanism. It has a “help me find things that won’t go to GBIF, or could go to GBIF, or did/will go to GBIF” mechanism, and it conflates that with whether something “Needs ID”. This proposal solves that conflation problem for both wild and non-wild observations in a way that keeps all the things in the same existing buckets. (Captive/cultivated stays over there. Wild is still right here in front of me, unpolluted by the riff-raff over there. GBIF-ability remains unchanged.)