Rap size confusion

Anybody else notice that the jointed shad raps, and the glass shad raps are one size bigger than the equivalent normal shad rap.

Basically, a #5 Jointed is equivalent body size to a #7 normal shad rap?

Any reason besides confusion?

If you took a number 5 shad rap, split it and added in a joint it would be roughly the same length as a number 7. That is the only reason I can think of. I agree, it is confusing though.