OK. So, yes, I agree that this doesn't seem to be working the way you would think. It's odd that it doesn't work for names with a large number of search hits, but it does work for names that have fewer occurrences. Fortunately, there are better solutions that will help you find what you're looking for.
If you just want to find that name in your watchlist, it's quicker to just sort your watchlist alphabetically.
If you're searching for potential Matches, you'll get the best results by using Search for Matches from that person's profile menu.
I can report this as a problem, but it's not likely to be high on the priority list. With a one-man tech department, programming changes are never as simple as we want them to be. ;-)