Microsoft does this for Windows apps if you don’t want scary warnings popping up everywhere. Apple doesn’t even let you sideload at all for iOS and for macOS they do the forced trash malware thing unless you run commands to allow the app in the terminal.
Am I missing how this is different from what we already have on most platforms? Is it because you can’t force it to install the apps? Is there not a developer mode that lets you install unsigned apps, or a way to root the device to install apps?