I dont see how it helps in a cloud environment? With correct permissions users aren't making changes to live servers or even logging in and if you want to roll out upgrades you can do it with OS images already?
Exactly, and if it's immutable, you know they aren't. Not through SSH, and not through a vulnerability either. I assume there's something you can hash to determine prove that you haven't been hacked, as well.
In some aspects, I'd hope that there are potential benefits on the security side of things as well. Since the host FS is generally read only in these type of distros, there is the potential to make some security teams happy.
Maybe it would help in a datacenter