The basic assumption is that if M1 talks with F1 for a long time, and M2 talks with F1 for a long time then M1 and M2 will talk for a long time.

Assuming it's based on hetero dating type situations, you can see why this wouldn't work. But there could be many other factors in play also. For example, if the M's above were talkers and the F's above were listeners, of any gender, you can see that two talkers or two listeners would not have a long conversation. But a talker and a listener is a good pair.

Instead they should look at this. If M1 talks to F1 and F2 for a long time, and M2 talks to F1 for a long time, then will M2 talk with F2 for a long time?

I think this would have a better chance of working.