I don’t think that’s accurate, but I’d be happy to see a source proving me wrong. I looked briefly, but wasn’t able to find a paper dealing with that alternation specifically (though I didn’t look very long, and there may very well be one).

Also, I’m pretty sure that for the dialects that do use “strong the”, they also use “strong a” in exactly the same environments, which to my mind makes it a non-issue.

Either way, there are plenty of other ways to get a word-final unstressed schwa followed by a word-initial stressed vowel, and we never see an “n” repair in any of those other situations either - the important point is that this is a process centered entirely around a single lexical item, and it doesn’t make sense for a process affecting a single lexical item in a common environment to be “easing pronunciation”.