My company just started requiring Microsoft Intune Company Portal app to use Teams and Outlook. From a friend in IT infosec at another company said the app can push apps, require certain settings, password requirements, or OSs, and can see a lot of stuff on your phone. I don't think this level of intrusion into my personal phone is warranted or ethical. Be warned. I'm just going to uninstall and suffer the internal political consequences.
Yes, if you want company data on a device then the company would be remiss to not want some level of control over that device. This isn't some big brother-esque conspiracy. They want to ensure you're not stealing company information or doing something stupid which might cause company data to be leaked or stolen by a bad actor. This is pretty common cyber security stuff. Now if the company REQUIRES you to have company data on your phone and does not have the option to provide a company phone to you then I can see a reason to be upset.
-someone who works in cybersec for a large company