The PC species thing is in a bit of a weird limbo, I think.
On the one hand, there are already species in 5e who are humanoids whose monster versions in the MM are not going to be humanoids. Crawford mentioned Gith specifically. And then he gives a bit of a fictional band-aid over it ("lost their other type") that is...less than satisfying from my perspective. Like, OK, sure, retcon that however you need.
On the other hand, there's no mechanical need to limit PC types to "humanoid." Constructs, fey, oozes (plasmoids) whatever, your type doesn't need to be "humanoid" for you to be a PC. So you can have aberration Gith who are still PC-relevant. It's just that none of the gith in the MM are like that - the MM entries are not meant to be used as player species. Hypothetically, we have some PC options coming down the pipe that are not humanoid being teased here. Great. But then why do we need the first story? Maybe just for all the species we're not really converting yet? For things like elves and aasimar and tieflings?
On the other other hand, there's something kind of exciting about there being species of multiple types. They talked about fey goblins and humanoid goblins and aberration goblins. You could also have construct goblins and fiend goblins (barghest?!) and dragon goblins and elemental goblins. There's something kind of cool about the various stories that encourages. You can imagine a diversity of goblins, from the martial drudgery of the Maglubiyet sect of fiends to the whimsy of the fey tricksters and then you have maybe aberrations for the psionic Blues in addition to those mutated by the Far Realm. Expand that to other creature types and yeah, that allows for some neat things. You can also have humanoid versions of other creatures (gnolls who are less fiendish, but also humanoid versions of dryads or humanoid versions of harpies or whatever) - things that are a little more in line with PC capabilities, regardless of if there's a PC species for them or not.
On the other other OTHER hand, 5.24 is consciously limiting the effects of species on gameplay. They blend them all together in the '24 PHB. Type isn't a big change, but people definitely miss some of the more impactful elements of species in general. So 5.24 could use a way to make your dwarf or elf or tiefling or aasimar or goblin or githzerai truly distinct from other races, humanoid or otherwise. Not something I expect the 5e MM to solve, but maybe something they're thinking of with this foreshadowing of non-humanoid PC's.