I think the Brookies must have so much competition for the available food that anything and everything is considered fair game. They surely do hit a dry fly with avengence. I have seen the time on Michigan streams that during a hatch they don't seem to want a surface fly. I can only assume they are taking emergers.
They are great fun and deserve to be released to fight another day. I'm sure the GSMNP streams can be as overpopulated with small ones as the Michigan streams but I could never keep one.