The thing is a model trained on the same input as current models except Quake and Quake derivatives would not generate such code. (You'd have to prompt it with descriptions of quake physics since it wouldn't know what you mean, depending on whether only code or all mentions were excluded.)

The quake special behaviors are results of essentially bugs which were kept because it led to fun gameplay. The model would almost certainly generate explicit handling for these behaviors because the original quake code is very obviously not the only reasonable way to do it. And in that case the model and its output is derivative work of the training input.

The issue is such an experiment (training a model with specific content excluded) would cost (tens/hundreds of?) millions of dollars and the only companies able to do it are not exactly incentivized to try.

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And then there's the thing that current LLMs are fundamentally impossible to create without such large amounts of code as training data. I honestly don't care what the letter of the law is, to any reasonable person, that makes them derivative work of the training input and claiming otherwise is a scam and theft.

I always wonder if people arguing otherwise think they're gonna get something out of it when the dust settles or if they genuinely think society should take stuff from a subgroup of people against their will when it can to enrich itself.