As a developer and a huge amorphous lover for 10 years now, my theory is that RazorQueen spawns after discovery all amorphous together with some random seed (ie 35%).
It just makes sense, from a game design point of view: RazerQueen is a reward for the player who kept playing the game until the end and appreciates the deep of this game.
From a game developer point of view: we are f*cking lazy, the faster way to add this "bonus" amorphous would use the red queen condition along with something that we already keep track and add some random seed to make it even rarer.
I'm absolutely sure that numbers of killed Biters don't have influence the spawn of the RazerQueen in any degree. This game has a truly well-crafted game design, having some random factor like this one decide how the final and most important "amorphous" appears would break the pattern how this masterpiece is designed.
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