That seems like just a fancier way of expressing TWIV's "we can't possibly know anything without lab experiments that establish the exact mechanisms, so we should do nothing" philosophy.

The undeniable fact is that this variant has successfully replaced other already highly prevalent variants. That needs to be explained somehow.

Could it be a founder effect? No.

Could it be random chance? No. Of course a stochastic process could converge like this even with no selective advantage eventually. But the change has been too fast and too consistent in this case.

Could it be a super-spreading event? No. The change has been continuous, and a single event would cause just a step-change in relative prevalance.

Could it be the new variant being more transmissive, or having another similar selective advantage? Yes.

Could it be an unspecified emergent behavior? I guess it could. But how are we supposed to reason about something that vague? We have a simple explanation that's consistent with the known facts, I feel that anyone proposing that it's just emergent behavior should be at least a little bit more specific.