I'll tell you what I find interesting. I just tried your experiment, but I never actually clicked "search", because I noticed that my "Sort By" is set to "Time: Ending Soonest". I then pulled down the list, and I do notice that "Best Match" is one of the options, but NOT the one I'm getting by default.
I think it's because I saved the URL long ago as a bookmark, and the URL contains "Ending Soonest" as the search type. Here's the URL from my bookmark:
I suspect "sofindtype=13" is "Ending Soonest".
Now, if only one could spread the word to the millions of eBay buyers to bookmark their search link set to anything other than "Best Match"!