Default Baseband an Kernel related question

I'm sorta new to all the android baseband and technical terms, but I've noticed some weird things with 2 roms that I flashed on my phone. Even though the developer says both roms are using the same baseband and kernel when I flash the rom this weird thing happen:

For one of the roms my phone is just fine, but when I flash the other rom my phone says, "Baseband unknown" even though everything else is the same.

Why is this happening even though the developer says both roms are using the same baseband and kernel. Any help?