Sounds like we are forgetting that YSU is on an equal plane with all 4 of those schools in all sports except football. Yes YSU is a DI program. In fact I was at an OSU vs YSU game where the Guins won handily. It was a return game from a rainout. As compared to football, it is very easy to schedule a p5 school in baseball. The SEC and Big-12 teams are quite profitable in baseball and those teams paying YSU expenses would not surprise me at all, but I am not say8ng this happens ... as I have no idea. pretty much all of the other conferences make much less money off of baseball.
I will tell you this, it is a shame the lack of support that the Tribe (and MLB in general) gives DI baseball.
Uaually when you see a single game, that is accomplished by catching a trip between two other team playing. For example Xavier might be on their way to a required series up in the NE and may catch a one-off YSU game.
Also, most of the big series are in early-spring, where all teams are desperate for competition.
Also, YSU get arrangements that stem from football money game ( like out 2 games this year against Illinois, which I bet are tied into some sort of compensation.
Scheduling in any small college sport is a tremendous skill.