I believe you are mostly correct. Indepth information on previous as well as current iPods can be found here:bennetsaysargh said:some clarification here.
to my knowledge, apple had the 10GB introduced in march 2002 with the scroll wheel and the same thickness as the 5GB. then at macworld of 2002, the introduced a touch-wheel 10GB that is slimmer, and the 20GB. maybe the 10GB was always thinner than the 5GB, but i'm pretty sure it went how i just said. please, feel free to correct me.