I think they wanted the excuse to call a Fighting user Rocky but felt roadblocked because the pun of his name works way better with a Rock type user. And therefore not only didn't make their joke clear but also didn't make any sense in the process.
They put a Blackbelt named Rocky in Black 2/White 2. Bonus points for them putting a trainer in the same cave named Blackbelt Drago.
https://dl.dropboxusercontent.com/u/82442627/Adelle.png I draw lolis :D https://dl.dropboxusercontent.com/u/82442627/IsawaKiyokoAlternate.png
Lance's whole team is part Flying in G/S. But wait, what type of trainer is he?
That's due to the lack of dragon types at the time. In this case there are plenty of usable rock types. I'm not saying all of his pokemon have to be rock type, just that the majority (or at least half) should be.