The math is the math, so can’t debate that
But would like to add some context:
-Swapping Smart for Lebron is undoubtedly a downgrade defensively that compels the other 4 players to take on oversized roles
-But the same is applicable when swapping Smart for any other starter
One thing I do at times is look for secondary costs/benefits of a player. Basically, do their teammates Net Pts go up/down with them on the floor?
I looked at the Lakers and the answer was No - except on D with LeBron. His teammates' DRTG has been 10 pts worse w/him on.