I don't understand. How does this answer the question of why women often hunt less than men? Or why typically men preferentially hunt and women preferentially gather? You say that "What was asking for explanation was the common belief that most societies naturally divide labour so that men hunt and women gather", but I don't see where in the thread anyone asked for an explanation for that. [And "ethnocentrism" fails miserably as an explanation for that anyway, since Western society doesn't divide labour into hunting for men and gathering for women]
In fact, I'm triply puzzled:
a) you seem to want to talk about why people believe a thing rather than why the thing is the case;
b) your proposed explanation is in any case i) unfalsifiable, being equally able to explain anything, ii) unsupported by any evidence and prima facie highly improbable, and iii) fails entirely to explain the phenomenon under discussion (to some extent "ethnocentrism" may be an answer to why people think that it's natural for men to work and women to not work, or, if we include for men to obtain and women to process, but certainly not, in the west, for men to hunt and women to gather!);
c) in the process, you state that the belief is demonstratedly false, while seeming accepting the facts that demonstrate that it's true! You said yourself, indeed, that it being true was "pretty common" in hunter gatherer societies (and surely nobody's ever claimed this putative principle was 100% universal!).
And indeed the evidence supplied so far goes further: out of 855 societies in which hunting was important, 841 of them had hunting as a male-only activity, and 14 of them had hunting as a preferentially male activity. None had a bias toward women in hunting. Zero.
Similarly (but to a lesser degree): out of 470 societies, 246 had gathering female-only, and 129 female-mainly, alongside 59 egalitarian, and only 36 preferentially or only male.
For the sake of simplicity: that's a 100% of societies with a male sex bias for hunting, and 80% with a female sex bias for gathering (with most of the remaining 20% being egalitarian rather than male-bias).
That looks like pretty good prima facie evidence for the idea that "most" societies naturally divide labour this way. Which rather does away with the need to explain why many believe this. [Indeed, since our society doesn't act like this, and most do, the belief that most do is doubly inexplicable through 'ethnocentrism']
Now of course, you may have better evidence than the Ethnographic Atlas. But the convention is that if one person puts forward evidence, you put forward your own, or you at least say what's wrong with the evidence put forward... you don't just sit silently as the evidence is presented and then carry on as though it doesn't exist.
So, and I don't mean to be harsh, and it wasn't my word, but: yes, a one-word response to an unasked or tangentially asked question, that doesn't pay heed to the gist of the discussion, that doesn't engage with the presented evidence, that isn't presented with any evidence of its own, that makes no rational sense, that has little if any explanatory power, and that could just as easily be presented as an answer to any thread on the board, can sometimes qualify as "underthought".
[I also think it's disingenuous, because it moves the discussion away from facts and toward political conveniences, by using political weapons designed to delegitimise the opinions of others without having to have recourse to reason or evidence. It's a Godwin. "People think like that because... because they're doubleplusungood people, that's why! And any sort of attempt to defend it is also doubleplusungood!". Slogans, dogwhistles, and politically loaded labels should be used a last resource, not as a first.]
But the river tripped on her by and by, lapping
as though her heart was brook: Why, why, why! Weh, O weh
I'se so silly to be flowing but I no canna stay!