I think you give Siri too much of the benefit of the doubt when you say that Siri understands your request. You may be correct, but maybe Siri just looks for a location like "McDonalds" and most of the time just shows you a list? It's easier when you're ignoring the rest of the sentence as if it has no relevance to improving your response.

It's very hard for us to discuss Siri's internal state; by contrast it's easier to discuss Google's observable performance, which is to semantically differentiate between these two requests.

You can just ask Google, "Nearby McDonalds" and you'll get a list. "Go to the nearest McDonalds" and you get navigation.

Take me to the nearest McDonalds - gives me a list.

“McDonalds” - gives me a list.

“Take me to the closest McDonalds” - brings up maps and starts navigating to the closest McDonalds.

After further experimentation. Siri doesn’t understand Nearest but does understand “closest” to mean that I don’t want a list.

If you said “take me to” an not “show me a list” then it actually did the wrong thing by showing you a list. I suppose “not working” is technically an interface choice, though.