I think this isn't complicated if you realize that Spider-Man: Remastered is being treated as a seperate game

MM PS4 -> MM PS5 for free

$70 -> MM PS5 + SMR PS5
or
MM PS4 + $20 -> MM PS5 + SMR PS5

SM PS4 -> SM PS4 on PS5 with BC

— Nibel (@Nibellion) September 23, 2020