I used no$ because it was simply the best emulator available back then (circa 1999), plus the company didn't feel a need to actually buy a dev kit since I was fully capable of building my own, and actually preferred to use, using open source tools (assembler, linker, make, etc) and no$gba.

We were publishing through Mattel for those games as a 3rd party developer, so they handled all the dealings with Nintendo and I assume they had an in house dev kit or two, or at least it was just a 2 gorrila relationship.