I've never heard the bluff variety before

Likewise - which goes a teeny little way to suggesting this could be a US variant.

I think I'd assumed the "buff" to be the bumping up against people the "blindman" does - as in buffeting .

M-W's etymology of buffet is interesting:

Etymology: Middle English, from Old French, diminutive of buffe blow
Date: 13th century
1 : a blow especially with the hand
2 : something that strikes with telling force