I think prompting people about things they probably don't understand is a recipe for bad user experience. My goal was to help people do the right thing even though they may not understand what the right thing is. The article is so that the more technical people can understand what is going on and make informed decisions of their own. I agree that renaming pages is much more common on newer pages that is why we do have it enabled by default.
I do have an item in my project tracker that I think would be a good solution when I can get to it. The idea would be that if you disable the url suggestion for existing pages that are renamed, then in that case we could add a little link that says "Suggest New Url?" so that it would not change the url by default but you could click the link to make it suggest a new url.
I don't know when I will get to it, its kind of a gold plating item compared to other things that need to be done, but it is in the project tracker and eventually I will get to it.
Best,
Joe