It isn’t bein hazmanim in any American yeshiva until rosh chodesh. And it isn’t rosh chodesh yet (I don’t think).
In any event, maybe they needed to go somewhere and weren’t able to daven with a minyan. It happens.
Girls think minyan is this hugely big deal. For many guys, meh. You win some, you lose some, you get plenty of chances. I ain’t talking about what it should be–I’m talking about what it is.
This often comes up in shidduchim, where a girl’s side will want to know whether the guy goes to minyan on time every day. It is a silly irrelevant question, and should not be asked. If you want to know whether he is responsible and productive- ask about something else.