I believe it, I've just never seen it done here. There's no reason for them to prevent bunches being split up, as I said they are universally sold by weight here, it's perfectly acceptable to purchase a single banana.
My local Target store has a small grocery, which stocks bananas in normal bunches.
However, they only have self-checkout, and no scales built into the checkout terminals, so you have to specify bananas by integers, even though the weight of an individual banana can vary considerably by nature.
All other normal groceries in my neighborhood use weight for bananas and other produce.