Penn has some dual major degrees that can take 10 semesters to complete - that's what Bernardini did to be able to play his 5th year if I'm not mistaken.
Not all schools support this and require the player to take a season off from academics. If I'm recalling correctly, Rosenberg took a year off at Columbia to retain his 5th year eligibility.
But yes, if the player graduates - or even if he should have graduated - then he's ineligible in the Ivies. You can't compete while working on a masters.
In your last semester, whether the 9th (football) or the 10th ( B.B.) you only have to take as many courses as you need to finish your degree ( eg not the 4 required normally each semester of play by the NCAA). It’s pretty easy to manage.
Again certain Ivies May have special rules that would prevent this.