Karl considered the information that the Special Forces team had presented him with. If it was true that the quality of the diet limited a monster's growth, it made perfect sense that most Windspeed Hawks never made it past the Awakened Rank.
Their favourite food was the Earth Mouse, a Common Grade monster. Eating that every day would give them a steady source of nutrition, but of a limited quality. If they were going to advance further, they would need higher quality food, but their usual hunting targets couldn't provide that.
They were capable of hunting larger targets, but larger bodies would bring scavengers and other predators, which would interfere with their usual hunting grounds and force them to move.
So, they would end up trapped in a vicious cycle where they could only rarely eat higher quality meals, and they would slowly grow to Awakened Rank as they got older.