I don't see what's the problem. The "default" program is the program that opens up when you click on a file with the particular extension. Int he case of a browser, if you have a .html file and click on it, your default browser will open up. Alternatively, if you click on a web link in some other program, say in Acrobat, the system will open that web page in the default browser.
Personally, I don't care about it since I don't keep html files and I don't allow Acrobat to access the Internet. Unless that's important, I don't see what's the big deal about the default is. In fact, I never use IE - or Edge, whatever - but I also never change the default, I don't see why would that be important to me.
As to following the money - I believe that's the right reason for them to complain, but since I don't care about other people's money (only about my own money ) , I am not usually following these "wars of words" and never cared for the N version, even though I live in the EU.