Very hard to say: it could be literally any app which has location permissions and is able to run in the background, including one of Google's or Samsung's system apps. Though if it turned location on that should narrow it, since few apps have the ability to change that setting, so searching for apps with the permission to change system settings should give a short list of suspects. The fact that it disturbed your YouTube sessions is surprising though (unless it was YouTube itself - though that shouldn't have the permission to change the location setting).

BTW "read phone state" isn't the same as "make & manage phone calls" - specifically it doesn't give the app permission to make calls. "Read phone state" has many uses, but a common one is that media apps need it in order to mute when a call comes in.

 

Those are settings within Settings > Location, but they aren't separate apps on my phone (Pixel 2, Android 11). I expect that both of those are "on" by default, though I turn "Location Accuracy" off myself.

But there will be system apps that have location permission by definition. For example, you can't deny location permission to Google Play Services, you can only turn location off completely (Google's location service is part of Play Services, so if you have any app that uses Google's location service then Play Services has to have location access).

"Google Location Accuracy" is misnamed anyway: it's the setting that turns on wireless network location, not something that improves accuracy (at least not if you have a GPS fix - if you haven't then even the crude location you get from networks is more accurate than nothing, but if you have a GPS fix their contribution to accuracy is negligible). But it is a setting that is very easy to turn on without knowing it: any app using a particular Google API is likely to feed you a pop-up when you use it that tells you "For a better experience, turn on device location, which uses Google's location service". That's designed to sound like you have location off, but it really means "enable this setting" (if you have location on but that setting off it means you only use GPS for location). I particularly hate the dishonesty of this pop-up because if you go to Settings to turn this on there is a disclaimer that tells you that enabling it allows Google to track your location, but if you touch "OK" on the pop-up, which is already deceptively named, it just turns it on without showing the disclaimer.