I didn't know they still made bi-focals.
I have been wearing vari-focals for many decades and have not found them to be any handicap at all for photography, whether using waist-level viewfinders, optical eye-level viewfinders or even EVFs.
One misconception that I frequently encounter in discussions about taking photographs while wearing specs (not directly related to this thread) is that an amazing number of folk seem to have forgotten what we all knew when SLR film cameras were first introduced - i.e. that the viewfinder shows a two-dimensional image on a ground glass screen (or its modern equivalent). So, if the viewfinder dioptre adjustment is correct (in my case, to suit the "distance" area of my vari-focal lenses) then, if the viewfinder image looks sharp, so will the photograph. Incredible how many people think that, when using a reflex viewfinder, your eye is actually focussing on the subject via the viewfinder and the camera lens.