Imagine if instead of NYC this was a small town, and a paper mentioned that even the mayor of the town stops in a certain store to get bagels every morning or whatever. Is that a partisan message?
At least to me that's just a human interest element. The mayor is a notable person, it suggests something about popularity and ties it to a name the reader already might know. It's the same as saying a celebrity shops there or whatever.
This case is a little different because NYC is a big city, but what's partisan about it? They don't mention his politics or views at all. He likes a sports team and he likes this shop. It's being mentioned as a human interest detail, because he's a minor celebrity with some readers. This is why it seems like you have some kind of political opinion about him - if you didn't, why would it be notably political at all?
I don’t know. It’s a counterfactual, and you can make up any series of imaginary facts to present your counterfactual in a way sympathetic to your argument. The principle is the same: the mayor has zero relation to the content of this article. If you removed the line in question, nothing of substance would change.
Over here in our current universe, we’re talking about one of the largest cities on earth, and one of the most divisive political figures in the nation.
So yes, it’s both unnecessary and partisan. It’s an article about road signs. Exactly how unrelated does the article need to be before you’d accept this kind of thing as crass?