I think side loading is an important point. You can even side load apps on a Mac so Apple is going to have a difficult time arguing this one. It’s fine to not allow it by default and adding the extra steps to enable it.
I’ll admit I am torn on this. Before the iPhone really took off in the US the mobile carriers were in control. Does anyone remember having to pay for GPS and navigation and similar things through Verizon or whoever as add-ons? I do not miss those days, Apple (and Google) have done a lot to improve mobile experience since then.