Well that's fucking neat.
Steam doing it again.

Thank god finally

Note that this requires both support from the gamedevs as well as mod creators

There's likely to be a large amount of growing pains around this upon first implementation. Especially Paradox games that keep around so many beta branches, there will likely need to be a lot of work done to ensure this works properly moving forward.

about a decade late. but as they say, better late than never

I don't think they know what version control means; this is more version tagging.