They already explained what the in-world logic for the humanoid vs aberration gith is. The gith who've spent most of their lives away from the usual gith home planes can be humanoid. So, Lae'zel from BG3 has lived the majority of her life on the Material Plane, hence gith like her would be humanoid. The same logic applies to the other creatures who were largely humanoid in 2014. So goblins who've lived or maybe descend from goblins who've lived on the Material Plane can be humanoid. It's the exact same story reason why elves are humanoid and not fey.
But the gith on Faerun were modified by Illithids just like the Gith on the Astral or Limbo. It is not their growing up in the Astral or Limbo that makes them aberrations but the Far Realms illithid modification connection, correct?
It is not like if a human had a background of growing up in Sigil they would no longer be humanoid, is it?
I feel like a lot of people repeating the explanation given in the video don't realize that Gith
don't grow up in the Astral Plane at all - time doesn't pass there, they
all have to be moved and raised on other planes. It seems like Crawford also forgot that detail during the explanation and was just using Gith as a non-fey example when put on the spot (and wasn't really thinking about how Gith in particular break that explanation). The Gith being raised outside of the Astral is not lore they've moved away from, either - it's mentioned specifically in the new DMG.
Lae'zel genuinely hasn't spent any more time on the Prime Material plane than the average Gith from her Creche, because Creche K'liir is, in fact... also on the Prime Material Plane (it's built into a large asteroid in the Tears of Selune, which are floating about near Toril's moon).
It is separation from the source that is important. So elves have been away from the Feywild so long they are no longer Fey. Humanoid Gith have been influenced by other forces enough that the Far Realm influence has been diminished enough or eliminated and they are no longer are aberrations. Personally I would make all Gith Aberrations or Humanoids, but that is the company line currently.
I'd either do this or make them Humanoid Aberrations. I don't really like the Humanoid type at all, TBQH, so I'd probably rather make them all Aberrations than all Humanoids if I wasn't just giving them two types.
Actually that is not what they are saying. They are saying NPC and PC Gith can be either. The PC rules currently represent humanoind Gith and the 5e24 monster rules currently represent aberrant Gith. But it could be either.
I think the company line is they can be either. WotC may only present one option in "official" material, but that doesn't preclude the other from existing.
I don't know if they've said something else about it since, but in the video about fey it was presented as "when you pick a playable version of this species, you are picking the version that has become humanoid and 'lost' the essence of its other type."
i personally don't like the "the PC species has lost their type-ness" explanation, but I don't have to follow it, and I wouldn't make my players follow it. It's a generic flavor explanation for a mechanical design choice - doesn't seem like what I would call a 'company line,' so I'm not sure we really know what the WotC 'company line' on this is officially. I wouldn't treat Crawford's interview minutiae in isolation as a company line in any case, but if they were... it'd be the aforementioned "the PC species has lost their type-ness."
