Do you agree?

Yes, of course. That's trivially true and not in dispute.

I still think you're rather missing the point, however. I don't see how it makes sense to object to the phrase 'mostly attributable' when that's a premise of the hypothetical. Let's look at the original comment in context:

E.g. I've often heard it claimed that the difference in average pay between women and men is mostly attributable to differences in ambition and time voluntarily spent at home with children. I haven't looked at the matter enough to know if this is true. But if it is, then denying any population-level differences between men and women seems harmful, because it implies that something that actually has an innocuous explanation is because of discrimination.

That is, IF [the difference is mostly attributable to something innocuous], THEN [denying population-level differences seems harmful]. That's all that was said. Kaj_Sotala never claimed the innocuous explanation was true.

Editeditedit: I apologize for my horrible social skills.