If I sit down to tie Thorax Duns size 14 and I size my hackle for a 14 hook, have I already made a mistake?

Most Thorax ties I've seen require wrapping the hackle on top of the hook which has already been wrapped with dubbing towards the eye of the hook.

Since the effective diameter of the hook shank has changed slightly, should I be measuring my hackle for Thorax Flies one size smaller?