If you use the technical definition, BS is not a mouse coaster. It'd be called a junior coaster. You'll also see SM occasionally referred to as a mouse coaster or mouse-style coaster (even though it doesn't fit the definition either). Best guess is that these all have similar thrills (going back to the OP) - small profiles, small drops and lower speeds than traditional coasters that are spread out, go faster and have big drops. So the terminology gets lazy. Plus it's Disney - we want any excuse to call something a mouse.