You are arguing that. He doesn't.

What I see argued there is the tendency for women to prefer something like early childhood education or psychology over software engineering.

It has nothing to do with suitability at all.

See also: Why Brilliant Girls Prefer non STEM Subjects[1]

The studies it cites show that women who are good at math (SATs, I think) also have good verbal skills, so they simply have more options. And apparently people of either gender who have both options open to them prefer non-STEM.

That is even an ability difference (whether biological or not is irrelevant, though SAT scores appear to have a strong genetic component) that has nothing to do with women being "less suitable" for STEM and yet fewer women in STEM.

So your logic that any type of argument, even if it's just preferences, has to automatically mean that there is a claim (if hidden) women are less suited is quite simply wrong.

Apart from the mistake pointed out elsewhere of taking a statistical argument about populations that tries to explain population differences (and not individual differences) and turning it into exactly the essentialist argument you find objectionable.

[1] https://www.psychologytoday.com/blog/rabble-rouser/201707/wh...

No, you're making the same mistake racists and antisemites make - you're trying to turn a generalization into a rule about individuals. You can't go from the group to the individual. If men are stronger on average than women (this is an incontrovertible sex difference) that wouldn't mean that women are unsuitable to be in a profession that involves strength, because differences within groups are larger than differences between groups. A particularly strong woman would be stronger than the average man.

Similarly, a disposition that applies generally to a gender doesn't mean that gender is suitable or unsuitable - suitability is a term for policies that get applied to individuals.

So next time my partner wants me to help with household chores, I can cite my well-documented disinclination towards the task to excuse myself as being fundamentally unsuitable for it?

Dictionaries define "suitable" in terms such as "such as to suit; appropriate; fitting; becoming", which all either carry a moral connotation (appropriate, becoming) or one of capability independent of volition (such as to suit, fitting). Let's not forget that one of the primary underlying moral motivators of the fight against sexism/discrimination against women is freedom (it's not an accident that "emancipation" means "release from captivity"). To turn, in this context, a statement that says that women do not want tech jobs into a statement that women can't do tech jobs (with a connotation of "even if they wanted") is not just a minor cosmetic change - along the axis that matters, it flips the meaning of the memo upside down.