you are correct. All true.
But there are no easy to implement groupware, open office, email, chat suite. Yes, in hn you can say zoho or sogo or libreoffice. While I totally use OSS, it is a pain for Universities to find talent to implement this at scale.
Also a majority just use MS products and want compatibility. This is similar to tons of devs doing OSS dev but using MacOS (and using VM or remote ssh) as they want their devices to run for 12 hours on battery.
Some European universities tried going open solutions - this patchwork either failed or some even got hacked.
At the end, there are no easy solutions. I sincerely wished some one like Linux foundation implements a total OSS solution based on nextcloud to build all integrated suite to compete with G-suite or MS.