Jumping into the girls/women debate.
Yes there are informal uses of girls. When my wife has dinner with her childhood friend group, it's usually referred to as a girls night. It's very informal and perhaps "ladies' night" would be a little less infantalizing and "friends night" would be not infantalizing and also not gendered. But most people probably will go along with that social norm of girls night. It is extremely informal for one, bit also used in a context of a close knit social group collectively by them.
The OP question was awkward though in the way it was used, down the fact that it went from "women's volleyball" to "our girls" language. If the sport can be termed in the frame of women's x it definitely ends up coming off extremely misogynistic and infantalizing to switch to "our girls" in the possesive when then talking about the athletes in said womans sport. They're all accomplished adult women athletes. It's not really a question of formality or anything, it was just written in a off-putting way IMO.
Personally I do find the girl/guy/boy language awkward at best. If someone says "a girl I work with" a lot of people find that language acceptable (though I defer to woman in these examples). Most though would probably find it extremely awkward to say "a boy I work with" because we have a informal gendered term "guy" for adult men that doesn't play double duty of referring to children too. I guess lady could/should fill that role, but people use that with a lot less frequency for whatever reason. Of course you can always just go with non gendered "my co-worker" in this example, but the most common language of girl/guy is clearly a unique standard.
Anyways the polling on these gendered terms doesn't show huge difference in mens/women's attitudes with women finding both girls/boys as slightly less accepting. So anyone here is entitled to their opinion without needing to fill a gender role to legitimize their opinion, but there's pretty clearly a different standard used for these gendered terms whether it used plural collective or to refer to individuals.