When I was a kid the local pet ranch (LFS) kept a RBP in a 10g. It was there for many years. Nobody though anything wrong of it. So one could be kept in a ten gallon, for many years IME. Though it would suck for the RBP.
come on now bro...you're suggesting stunting a fish because a local shop did it? we've got shoaling fish (i use the term loosely in this case) that should shoot up to 6 inches in the first year plus messy eaters, no way it should be in a 10 inch wide tank for years