Depends where you are. I can’t speculate on the EU or its member-states. But here in Canada, your information is basically stuck at an organization unless you give consent to have it sent somewhere else. And it gets even more complicated when it involves a provincial-federal relationship.
Personally, I think it depends on the sitch. Something immutable would probably be the better go for people coming from Windows and would help with IT costs since all systems would be, at their base, the same. No one is going to accidentally install something that breaks their system. And the main drawback of immutability (less control over the system) wouldn’t be a problem because people shouldn’t be installing things on government systems that are outside the scope of their job.
EDIT: In a sentence: a good distro is one that’s good for your organization.