I understand what you're saying, but I don't think they did exactly what you say.
Mike has said very often that whenever the band heard an idea that sounded like something they did before, they felt bored with it. It's not like they said oh, that sounds sort of like Hybrid Theory, get rid of it right now. They're just bored with that sound/they don't like it anymore.
The fact that song ideas that sounded like older stuff even came up in the first place shows that they weren't placing boundaries on themselves, they just didn't like any of them.