the minimum amount of rounds for a swiss event is equal to "n"
the number of participants = 2^n
Now, assuming that we have "n" rounds in a swiss event, yes, it will take an unbeaten record to win. However, if the number of rounds is greater than "n", then one loss will not necessarily prevent a person from winning an event. In the swiss tournaments where I play, very rarely does the winner have an undefeated record (no losses). It's good to have more than "n" rounds, even if it's only "n+1", because it discourages people from dropping out after they receive one loss (though they should continue playing for SotG and because it's fun). The less people that drop out of a tournament, the more "accurate" the "Strength of Schedule" tiebreak method will be.
I think it would be better if they used "Time of Loss" or "Cumulative" as the first tiebreak method and then refer to opponent's records as a second method.