RPGMemes

As it happens I've just looked up the 5e rules for this for the sake of another comment, and their rules are that, like PF1e, if you go vertical, you follow the same rules (i.e., Chebyshev by default, optional alternating) as on a flat plain.

I've not looked up the PF2e rules, but I feel safe in assuming it's the same in this regard as 1e.