For males that is definitely possible yes, rootbound can indeed cause stress and let the plants show sex. But in this case looking at the plants they look rather healthy and you use, what, 3L pots? Shouldn't be an issue normally. Might be a case of males with a lot of testo wanting to show their balls to the world LOL
Could also be a genetical thing in these lines, which I don't know about, but as long as it is just a few balls here and there it could be the normal display of masculinity ;-) If you really see full male flowers appearing, than it would be an issue in my opinion. Please keep us posted mate, always good to see feedback from you, cheers