There are many reasons to isolate, jealous boyfriends or other men are one, guys who approach a group without any isolation will usually be chased off by somebodies boyfriend or "Is this guy bothering y'all?" guy. A threat is a threat, point blank.
I think we've reached a point where you can freely announce your intentions, when you do that you can almost expect one of them to ask "How much you make a year?" or ask about tax returns, the approach with many women involved means you have to qualify for all of them to isolate one of them, it's just unfavorable plain and simple, having a wingman shows you have some amount of social status which is a qualifier and sometimes enough, obviously the confidence is there but what's behind it?
I would say overall this is just a bad approach, I mean you can isolate but you could also do a handstand if she's just letting you isolate her from friends your basically in already.
Most guys will run with this "I'm just having fun" in a boring tone, not saying anything funny, just kind of lame.
One of my go to obnoxious lines is aimed at sowing a spark of competition between them, I'll walk and bump into their circle, stand in the middle and interrupt whatever they are talking about by yelling "Ladies! LADIES! Relax, there's enough to go around!" I've had women put me into a headlock, push me, hit me, it's just a great opener, sometimes I'll grab some random near by guy and claim he's my friend, just involve as many people as I can and make a scene about it, it's in my opinion the best way to separate the group of friends by just opening it up to the chaos of the club environment, but you really have to be a bad mother****3r to pull it off, gotta be ready to throw your hands up in submission, be lectured about being rude, maybe a joke, just get in there and create as much chaos as you can