Throwing a match just to possibly avoid playing a good team the next week? Some real fuck boi shit right there. If you're good enough to contend with the good teams in a division then you're going to play them sooner or later.
The pre-season week serves a couple functions. One is to give teams an extra week to iron out their rosters without any consequence. Putting together a solid HL team isn't easy and a lot of teams like having the extra room to make sure they're ready for the regular season. The other reason is to give the admins a decent idea of how to match teams up the first week. It might not seem important for a small division like platinum, but with the crazy amount of new teams in iron and steel how are the admins supposed to know how to match those teams up. A preseason week makes scheduling for the real first week significantly smoother and more manageable for most teams.