you're talking about the roster limits without considering transfer portal. like, divide the roster limit into the existing roster. you're not considering some schools might complicate that further by going the "coach prime" route of shipping out current rosterees and hitting the portal.
in math terms, if they currently carry 30 and have to go to 10, that seems harsh enough, 1/3 of the team is left, but they could also be looking at it more like, i will keep my 5-7 best, and fill out the remaining 3 from the portal and recruiting. in which case it's more like 1/6 or 1/4 of the existing team is safe, not 1/3.
i mean, if you think about it, most teams other than the worst D1s or D3s are already rostering 10+ people. they'd have to cut below 10 existing to enable any recruiting at all. otherwise you already caught your fishing limit before you start. you'd then have to graduate or lose people to have any new holes. unless you cut actually past 10 to single digits. then you have as many holes as you go past the limit.
last, i think as some have suggested this situation may tend to favor transfers or the best elite athletes. if i have 10 XC slots. then i can't carry hurt people or injury prone. then i need every slot to count. then my school can't be developmental unless it's the best recruits in the country. in which case i let some other school down the food chain, weaker D1, D2, D3, NAIA, take the chance, then swoop in from the portal.
and then like i said, if we're cut way down to 10, doing the portal means a few of those 10 aren't even safe year to year.