I actually think if you said "closest" or "nearest" and Siri just gives you a list, then Siri has missed out on useful information. You can also say "Nearby McDonald's" to Google and get a list, versus "Go to the nearest McDonalds" and you'll get navigation.
There are all sorts of ways to handle this request, but Siri's is the laziest, and in doing so asks more of the user's attention. If you just say "McDonalds" to either voice assistant, you also get a list. From that perspective, it's as if Siri ignores any information that might be gleaned from the rest of your sentence.
Siri learns from us but we also learn from Siri, and we might find that some words don't matter. You mind as well just say "McDonalds" if Siri is going to ignore the rest.