That's almost as a loaded statement as saying people who smoke weed commit crimes. Sure there are people that smoke weed and there are people that commit crimes, and some people who commit crimes smoke weed. But is there really any correlation between who smoke weed and people who commit crime?
For all those married couples that swung, was swinging the reason behind their divorce? Maybe they had problems stemming before the swinging. Or maybe they got divorced for entirely different reasons. It's true that some couples that engage in it might break up from it if they are both inexperienced and think they can handle it. But it's also true that is not the case with everyone.
I would seem that Masha/Sasha, and to an extent the 2nd couple are both extremely comfortable with it. I haven't seen the full video but there was at least one moment when the male guest was holding his girlfriends hand while he was fucking Masha, while Masha was kissing and hugging on Sasha at the same time. And even after the event, the guests had no problem having regular sex with each other and Masha/Sasha looked perfectly content sleeping with each other. I'd say they've all done it in the past.