@honongakungaku asked: "could you please elaborate on this?"
some things that frequently happen are:
they refer to these genders as "nonbinary" or "outside the binary" or otherwise make it clear that they are considering them through the lens of / using the frameworks of the European colonial gender binary.
they talk about how these societies prove that nonbinarism is "ancient" or "natural," which backdates and universalises the (in fact, I think, very specific) concept of "nonbinary" identity in a way that furthers the logic of colonialist gendered taxonomies.
they do so in order to prove a point about (read: white) nonbinary people being "valid," or to give historical precedent to the idea of gender not being a strictly assigned and policed binary by pointing out that the colonial gender binary is a recent invention—which would be fine, except it's often done with such a lack of effort towards understanding how the societies they're talking about actually function. because they're just rattling off a list to prove a point. so the violence of colonialism becomes lost, because they're just using the results of it (namely, the marginalisation of these understandings of gender) to slot neatly into whatever argument they were going to make anyway, without really learning about or describing the stakes of that violence (or how imposition of a gender binary was a tool of colonialism and thus enabled other kinds of colonial violence).
there's often a transparently sort of racist noble savage-ism to the whole thing. these genders are ancient and natural because "pre-colonial" people are obviously atavistic and living in a state of "nature"? the way that "third genders" are treated and conceptualised has always obviously been worthy of emulation, because Indigenous people are racially incapable of being prejudiced or something? there's nothing squeamish or uncomfortable or sort of shameless about speaking about Indigenous peoples as though they exist to be sources of inspiration and quasi-spiritual relevation to settlers and those in the Global North? the "third gender" concept has been criticised for this reason.
taking this tiktok as a representative example: they talk about "Native Americans" as one big group, apparently arbitrarily mix the past and present tense when talking about "Two Spirit" identities, and then say that these identities don't "fit in the Western gender binary" (emphasis mine)—as though, if "pre-colonial Native Americans" (their term) had understood gender in terms of a binary, they would have "fit" in the colonial gender binary? which completely misses how even people whom colonists sexed as female and understood to be fulfilling "feminine" social roles didn't fit the colonial gender binary, because colonial understandings of gender were designed not to "fit" them in order to further colonial violence. speaking as though Europeans just sort of happened to have a binary view of gender which other peoples just sort of happened not to "fit" is completely backwards and, again, elides the reality of colonial violence.
they refer to hijras as part of their rundown of "Where do Non-binary people come from?" with no reference towards or concern about how hijras today speak about their own gender, and no mention at all of the fact that a lot of them would call themselves women before "nonbinary"... because again, they're more concerned with how various understandings of gender slot into their argument than they are about these actual societies or people.
they repeatedly use words that they describe as specifically referring to people born with penises who fulfil feminine social roles as evidence of "queer," "intersex," or "nonbinary" identity? why can we backdate all of those terms, but "trans woman" is off-limits...?
again, there's nothing automatically bad about using various types of real-world evidence to support the argument "the colonial gender binary is a recent invention and not a universal law," but often it is done very very badly. and racistly. and by recreating anthropology-flavoured transmisogyny against Indigenous people. it does the opposite of helping us understand the relationships between race, gender, colonialism, transmisogyny &c.