I was confused by this too, here's why the Zips are already the champs
Tie breaker for MAC soccer teams
1. Between TWO teams:
A. Head-to-head competition
B. Division Record (10 games)^ (note: irrelevant for men's soccer)
C. Winning percentage* vs. ranked conference teams (top to bottom, regardless of division, vs. common opponents regardless of the number of times played)
D. Coin flip
So the worst the Zips can end is 3-1-1 and the best either WMU or SIU-E can end is also 3-1-1 (but not both because they play each other). If SUI-E ends 3-1-1 the Zips win on head to head. If WMU goes 3-1-1 it drops to the highest team in the standings that you lost to. Since WMU lost to NIU and there is no way NIU can finish lower in the standings than WVU (since the Zips would have to lose to them in this scenario) that is where the Zips eliminate WMU so they are the regular season champs and host no matter what happens tomorrow.
In any case glad to see the tournament back where it belongs ?