I'm sure they do, but the common traits of those three final smashes are too numerous to be coincidental.
they all three are VERY hard to control due to speed and lose flight controls. all three (except maybe diddy) do damage to enemies when you so much as touch them..(I think diddy's does as well ,but I think the bulk of the damage from his comes from the guns and the barrels crashing the stage at the end..none of the youtube gamers have figured that out yet...go figure)
Also Pokemon trainer's final smash seems to be broken; by that I mean if you took point blank damage from all 3 moves:hydro pump,solar beam, and fire blast you are screwed. But the solar beam seems to launch you into the air and drive you backwards. So the other two moves will miss you entirely since you're being juggled by the beam until the move is over r you can manage an air recovery to avoid the rest of it.
I can only see this move really being effective again st heavy characters since they likely won't get launched as high.