Well, it’s two different things, one is the background record, which is less “freaking out” and more “not for me on PC”.
The other is blending the background recording with metadata on a timeline, which starts getting Recall-y in terms of logging a video recording of what you were doing where there is also a data record of what you were doing. I do think that part starts stepping over to kinda creepy.
It’s more useful here than as a OS feature, though, because yeah, I can see it saving one the trouble of recording different matches separately or having to scrub back and forth to find certain things.
It’s not just the games that support it, it will also tag other metadata it knows automatically on all games, like achievement unlocks. And you can manually add tags, too. It’s all telemetry that Valve and the devs are already extracting from you, of course, plus whatever you volunteer in manual markers, but it’s still a bit creepy to see it laid out on a timeline like that.