Here is a short write up about how short range spawning works and the effects they have on the existing spawns. I also give Ludia some helpful advice on how to make them unterrible.
If the issue is spawn dilution, they could have added them as local spawns instead. After the introductions of Glyptodon, Andrewsarchus, Acrocanthosaurus, and Troodon, there are some openings in every local. Local 1 needs a new anytime rare and day epic. Local 2 needs a new anytime common and a new day epic. And locals 3 and 4 need new anytime commons and rares. Amphycion, Gorgonops, and Megistotherium could easily have filled some of those slots.
It would only delay the inevitable. But didn’t throttling the spawn rates of local dinos in proximity spawns make that problem instantly worse?
They could have added the new creatures to Locals, sure, but that doesn’t make the Global pool any less bloated.