Yup - the core idea is the same, only the "implementation" is the opposite.

I'm calling it "swapping" because, in some branches, what's currently reconstructed as *o ended as *a: for example PIE *h₁óynos "one" → Proto-Balto-Slavic *aiˀnas, Proto-Germanic *ainaz. So if his hypothesis is true, in those branches the mid vowel becomes the low vowel and vice versa; this does happen but it requires some specific conditions (like gliding, length, or some other secondary articulation), otherwise the vowels end merging midway.

*e, *a, *o, and then *ə (trad. *o) > *o, which might(?) be a more natural late PIE triangular vowel system that would then

On its own *a *e *o wouldn't be too natural, but if we include *i *u it does. And by then odds are that the later were already "promoted" to vowels.