This claim.
Does not support this one.
Since the exact method on you you’d reach any given winrate don’t impact what the ideal winrate you are trying to reach is in the first place.
In a multiball with 2 scum factions and the town with perfect balance would mean that when the scum teams try to go against the town, they succeed 66% of the time, and then when they do each of them have an equal winrate against each other. This is a 33/33/33% winrate scenario inspite of the factions working together early.
Remember, balance is ultimately just fiddling with the numbers until everything fits such that the game is as fair as possible. It can be done given enough effort no matter what the base is to begin with.