Doesn't know what? This isn't about the model forgetting the training data, of course it can't do that any more than I can say "press the red button. Actually,

Doesn't know what? This isn't about the model forgetting the training data, of course it can't do that any more than I can say "press the red button. Actually, forget that, press whatever you want" and have you actually forget what I said. Instead, what can happen is that, like a human, the model (hopefully) disregards the instruction, making it carry (close to) zero weight.