Not for me. Mine only allows Google. Maybe because I'm using a custom default search engine? If so, it should just use my custom one, and should obviously give me a choice regardless.
This may also be a bug in the Firefox app: I've just observed that when I change my default search engine in Firefox, that setting isn't necessarily reflected in the search intent handler until after I force stop Firefox.
Either way, to reiterate, it's definitely Firefox you're seeing here. If you don't like the way it behaves, I recommend following the other suggestions on this thread to file a bug report with Mozilla.
