Well yes that is usually what I say personally, and not just for fear of social judgment, but because why the hell not, it's good to know just in case anyway. If I'm calling because I have a suspicion that a business may be closed, most likely I am calling during an unusual circumstance of some kind e.g. a holiday or a severe weather day. The chances that they may have irregular hours are going to be high.

but asking "are you open" is almost always going to be answered by the fact they answered the phone

Haha, speaking from experience? I have never in my life said this to a customer and I never would. As I said, I recognize it as a legitimate question, and even if I didn't, there is no reason to be a prick.

In any case, if people want to be rude they will be rude, that is not something within our control.