That the term "sideloading" has normalized treating this as a special case is a problem.
It's unlikely the terminology can be rolled back at this point, but occasionally reflecting on this is useful.
We didn't need a different word for not being able to install an application on your phone without the permission of the company that made it. We needed a different word for the thing that was new, which is the company that makes the thing that you own refusing you permission to use it as you see fit.
Also, I think you'll be quite disappointed in what the general public does or does not care about. The iPhone has always been even more locked down than Android and it sells like hotcakes. Even on Android only a tiny minority of users make use of the option to install third-party apps. I think the general public should care about this topic, but all evidence is to the contrary.
in this sense i do actually agree about the misuse of 'sideloading' - the planned change would not impact just sideloading, but also 'third party' stores
Most people don't know what sideloading is because most don't sideload and don't have a need for it.