It's more like animations do not dictate the proficiency used, only the weapon type (outlined in red below) does.
Half-swording always uses polearm WPF despite having a 2h right-to-left swing.
Flamberge always uses 2h WPF despite having polearms left-to-right, polearm stab, and polearm overhead.
Langes Messer always uses 2h WPF in 2h mode despite having a polearm stab.
I don't think it's possible to have two different WPF used on the same weapon without X switching.