I looked at the schematic again and see what you mean. I don't know anything more than you, at this point. Someone at Weber should be able to clear it up.
I just ordered the assembly. The rep was pretty sure that the bowl was black. However, by the time I ordered a bowl and a handle to go with it, it cost more than the assembly, which also includes the ash ring; so I ordered the assembly.
I did look up a current performer, with a silver bowl, and the part numbers for the assembly and bowl are different, while the ring and handle are the same. I suspect the part numbers 65162 and 65196 are indeed both for black bowls.
I'll report back if this is not the case.