> Unless training included line-level skips

Yes, of course — GPT-4 was trained on all common character sequences, including linebreaks and other invisible characters.

You can see how it works here: https://platform.openai.com/tokenizer

Nonetheless it doesn't need to have seen examples of line-level counting before. The "concept-level associations" you mentioned are an emergent property of the model, it forms its own concept-level associations as a result of being trained on such a massive dataset. It's what enables it to output original content which has never been seen before.