Even calling it side loading is an attempt to delegitimise the practice. To make it sound like you’re doing something dodgy by the side.

It’s just installing an app.

Nobody calls installing an app from outside the Microsoft store on their Windows PC “side loading”.

Likewise for Macs regarding their app store, or installing an app from outside your distro’s repository on Linux.

Do you think the only thing TVs are used for is watching traditional terrestrial TV? Lol