You mean use regular season standings for slotting everyone except for the champ? So the person finishing 8th but winning a playoff round or two would still pick 13th?
I think there just is not a material difference between any of the slots for playoff teams (13-20). Pick #13 might be worth a wee bit more than pick #20, but certainly pick #33 isn't worth anything more than pick #40.
It makes sense to give the champion the last pick, so we just carried that logic down through the other two podium finishers, and then the rest of the playoff teams.
We could randomize pick slots for every playoff team except for the league champion. That might seem more fair, but then again, the playoffs are basically a randomizer anyway.