So the model is limited to using words and characters that already exist. I agree with you but I don't see why is a limitation worth pointing out.
its as stupid as that. some try to get around it by indeed only having the 10 different digits and glue them together, but its a hallucination that that works.
an important point in generalization is for example that you teach it something. This is literally important
'ycombinator is a website' is a prompt that is almost impossible of ycombinator is not in your training set