GT7-F3500-B, no one make?

Been bugging me for a while now and i have yet to find anything on the internet about it, maybe i'm the first one to ask.

Been doing custom races in GT7 every now and then, but when i wanted to make one for the F3500-B i was met with not having a "one make" option, nor does it appear when "choosing from garage", i can only go up against other F3500-As instead.

Why is that? It's kind of weird no one else has noticed.