It sounds like the criticism hints at the hidden node problem. (Briefly: One of the largest problems in wireless networking. A and B can hear each other, B and C can hear each other, but A and C can't. So when C wants to talk to B, how does it know if A is already transmitting and B's receiver is already listening? In large networks this gets hugely important.)
But it sounds like the simulation is already maximally pessimistic about it -- there's no RF attenuation in the drawer, so all the devices occupy the radio channel whenever they're transmitting. So I would imagine that software that works well in this case, would probably also do decently in the real world. (As opposed to software tested on a naively-simplified network of RF cabling and attenuators, which would not model the hidden node problem's complexities very well.)
So, while the real world will surely be more complex than they hint at in their sentence, I think the simulation drawer is also better than you hint at in yours.
There are nuances, of course, and frankly there are RF network simulators they could be using, but I think the presented MAC-filter approach is not terrible.