Her and one of her colleagues are the de facto git gurus in her entire department of over 100 people. She's ended up owning tooling in their build pipelines that is quite complex, using libgit, etc... That tooling was eventually exported around to the rest of the engineering teams (~1,000 total engineers). Now she gets random, challenging git (and perforce, to a lesser degree, and she stepped in to help with some SVN issues at one point in time, though those projects have moved over to perforce, I believe) questions from the entire engineering organization.
I do agree with you, though, that git is probably the wrong thing to focus on and that she and her colleague are outliers. But, it's interesting to see nonetheless.
Granted in any sane company this should just be done by the devs themselves. But as the OP said, in most teams knowledge about versioning, branching and version control is very very limited. Even if all you know is how to do a rebase of a longer lived feature branch easily in git (skipping the commits from the other branch) you will be the wizard that everyone goes to. Many many devs will not even attempt a regular rebase. It's black magic for them.
If all you desire is a cozy job in a large company with braindead processes and policies this sort of thing is probably enough to be tipping the scales towards: well we shouldn't lay off that guy coz he's the only one that can work the version control magic AND he codes like mad.
If you wanna stick out in a company filled with John Carmacks you will have to do better, sure.
On the flip side, you are now a source control/build system engineer, and it's pretty easy to get typecast as such (given the outsize impact your specialist skillset will have).
It's clearly just an example, but whether it's a bad one or not is debatable. Git is used by most shops, and most people have challenges with it at one time or another. Further, it is IMO an excellent example of how choosing the right data structure for a problem can have a profound impact on the resulting application. You could do worse for broadening your knowledge of ComSci than by a deep study of Git.
Maybe a better choice is something like CSS: there's actually a lot to know about it and a lot of companies need people who are good at it for their core product (even though it's not as deep a topic as say being very knowledgeable/skilled in functional programming).