I expect the employers would actually prefer to just give everyone a phone the companies owns. They are doing the work profile on a personal device because many workers strongly prefer that.
What would suck is if you're not allowed to bring your personal phone at all on campus. Then if you have to reach family you have to do it from your work phone.
Most places outside of tech folks with tolls need to carry company tools where they go - doctors carrying hospital beepers was essentially a meme in the 90's.
I think it's fine to choose to use a personal device, but employee education around personal devices is very poor - no one sits you down and goes through your rights as a worker and companies benefit by keeping those rights obscure.
You can accept the risk if it's worth it for you and that's fine - but a lot of people aren't aware of the risks and their employer certainly won't tell them.
Just have a phone with an obscure OS and escape all compatibility with their corporate crap. They should provide you with a phone if they want you to install their corporate app.