People are imagining this. It’s just the same old thing of people clearing mobs on one area of the map resulting in the max mob count for the map reaching its limit with spawns elsewhere on the map.
The spawn system functions based on having a map max limit for a monster, and many different areas a monster can spawn. For example, let’s say there are 4 spawn areas for a monster, you kill 4 of the monster in area 1, and 1 spawns in every area. After you’ve done this a few times you don’t have any more in the area that you’re in because they’ve piled up in the other areas you haven’t been clearing.
It’s a system to encourage people to move around a map when clearing monsters, not to stay in the same area.
The limit can also be taken up by any monster. So, if you’re clearing Truffles and don’t clear the other monsters on the map every now and then, you end up not having many Truffle spawns because all the other monsters are taking up the max monster count.
Of course, different areas also have different max mob counts too, so the effect varies slightly on a map by map basis. This however is why channel hopping in place and never doing anything on the rest of the map can end up feeling like you’re not getting any spawns anymore on every channel. You just have to clear the rest of the map to reset the effect.