I can see Microsoft moving to the same sort of thinking as well. Apple already made Mac OS users jump through hoops when you want to install something from the internet or even through a third party package manager like homebrew.

Not yet.

Not to defend it, but the first time I encountered the term was when BlackBerry released their Playbook tablet. It ran their bbos10 and they created an android emulator so you could run some android apps. The process of installing the apk into the emulator was called sideloading.

I miss BlackBerry is all I really wanted to say.

Windows laready has something like this it's called S mode i think. IT makes it so you can only instlal stuff frmo the windows store, but you can disable it pretty easily.