I think sideloading is a fine term when it is a consumption device. No one buys a video game console expecting to be able to install anything they want. As a matter of fact, there is an argument that restricting what can be installed is a feature. By maintaining control of the hardware, they can eliminate entire classes of problems that someone might run into. That is to say, when you let your kid play on the switch, you don't want to have to troubleshoot how they got the thing borked from installing malware.

That said, I do think words matter and I always point out that the reason these systems are locked down is because of Digital Restrictions Management. I also refuse to buy anything from Sony because they changed their mind about letting me install linux on the PS3.

I just think side loading is good way to describe installing custom software on a non-general purpose computer, and that not every computer needs to be general purpose. It's significantly better than the previous terms of hacking, cheating, stealing, and voiding your warranty.