[nullc]

The 'pattern matching' happens at complex layer's of abstraction, constructed out of combinations of pattern matching at prior layers in the network.

These models can and do work okay with variable names that have never occurred in the training data. Though sure, choice of variable names can have an impact on the performance of the model.

That's also true for humans, go fill a codebase with misleading variable names and watch human programmers flail. Of course, the LLM's failure modes are sometimes pretty inhuman, -- it's not a human after all.