I don't really see how the description contradicts the behaviour here. You could easily be looking to match a word starting with "a", in which case "a&" would be your one-word wildcard match.
As for which behaviour is more useful-- imho you have more functionality in being able to do something like "a& iswm abc" than not (see above example), so why change it? If anything, &a and a&b should work too.
