I'm not particlarly sure why you would say that. What makes you believe they are actively trading between themselves and what is your logic? I see no particular reason to expect that, particularly as an explanation for what goes on between the spread which I've actively covered. There can be trades between them if one has inventory from lower and the other wants it to cover because they misgauged the support and rising popularity of a stock. Otherwise, they are mostly trading against each other, not collaborating.
Of course it is made to present a preception. The MM's do it all the time. So who among us is to say we can not do the same. They sell 200 shares of a stock to send a message. They hit the bid to drop the preception of price. So we hit the ask to show them that we are on to their BS and there are more of us than there are of them. I got a message for them. Hit the ask. It does not hurt at this price. They can't send messages about a stock that keeps going up each day. We send the message that it is going up. Try it you will like it.