That's probably more or less what's happening. If the site is doing full-text search, and there are no exact matches, adding more terms is going to generate more and more partial matches. Some kind of re-ranker might be able to make sense of them but those are difficult to get good results out of, probably rarely employed by a run-of-the-mill commerce site, and might be drowned out by competing objectives (sponsored results, ranking by likelihood of purchase, etc.)