It supports them via the Super Gameboy code, but you need to keep in mind that it is not a dedicated GameBoy emulator, and that some games do not fare well in the SGB environment. You also lose multiplayer capability in that connection mode for some games.
I guess what I'm saying is that BSNES supports some GB/GBC games via proxy, and is not dedicated for such purposes. Having your page list BSNES as a GB/GBC emulator is very likely to do two things:
1) Make unknowing people think that it is in fact a dedicated emulator for the GB/GBC.
2) Potentially give Richard Bannister more headaches than he'd like responding to inquiries as to why X game isn't working like it did on that person's "real" GB/GBC. BSNES requires the Super Game Boy BIOS put in a very specific place, and does not come with it.
Also keep in mind that emulating a secondary system like the GB on top of the SNES architecture does up the system requirements some for BSNES. This isn't really too bad on modern computers, but could put borderline computers in a pickle.
KiGB is a good emulator to list as a main source for GB/GBC emulation. BSNES really isn't.
There are games though that do make use of the SGB for enhancements, so it isn't without merit. It's just that it's almost a guaranteed headache maker listing BSNES as a standalone GB/GBC emulator.