You are still oversimplifying, from what I have read. The Ivy reluctantly allowed players who would have been a senior the year that was cancelled to play this year. The rule that the NCAA has always had is 5 years to play 4. So it isn't really the Covid rule that is an issue. The Ivy didn't do red-shirt years and only gave players 4 years.
The problem is I am 99% sure that the Ivy is not permitting players who were not seniors in 2020-21 to play an extra season - i.e. their 5th year, 4th playing. So they only have had 3 years playing. It has to do with the Ivy's academic emphasis philosophy.
If anyone knows otherwise, I could be wrong, but that was my understanding and I assume factors into all this somehow.