There is no shortage of sketchy apps on the play store.
Through my personal bias I would imagine that most people side-loading apps tend to be people using F-Droid who know more or less what they're doing. Although I'm sure there are some people who blindly follow sketch website telling them to install sketchy APK directly. But do these people really outnumber people installing flashlight app from play store that steals your data?
All this locking down your device "for your own protection" assumes that the play store software is actually vetted and secure, but that second piece never seems to fall in to place.
This random article [1] suggests that 67% of malicious app installs comes from the play store itself. So this whole "Advanced Protection" scheme only protects against 23% of threats. Pretty weak IMO.
[1] - https://www.zdnet.com/article/play-store-identified-as-main-...