The only way I could see that happen is if quite a bit of the SAT would test for skills that can be practiced but don't correlate with g. Not very likely.

Not likely?? It's certain!

If you know the scoring rules and their implications like when to guess and when to leave it blank, that can get you points you might miss from leaving it blank and reduce your penalty on things you'd have gotten wrong.

If you know better how to manage your time, then you won't end up rushed.

Simply having done it before reduces the stress of the situation and can enable better focus.

Being familiar with the style of questions asked will help a lot - you'll know to expect certain odd phrasings that can trip up a naive test-taker, and in some cases you will barely need to parse, simply pattern-match. 'Yup, this is that kind of question.'

And that's setting aside just studying the words they're likely to ask you about.

None of these have all that much to do with g, and I can see them producing a swing of 40 points easily, perhaps more at the lower end (you know, in the case where there are hundreds of points to gain).

This isn't to say that intense SAT prep is a huge difference on average - it could end up inducing more freakout instead of less, it could induce someone to stay up late and not be rested, it may primarily be used by those who would already do well, it may be used as a crutch by those wouldn't... all sorts of confounding things. But the idea that there is no significant component of the SAT that's practicable non-g is hard to believe.