Of the two nncp uses transformers but isn't an LLM while ts_zip doesn't use transformers but is an LLM. Remember LLM just means large language model, it doesn't make any assumptions about how it's built. Similarly transformers just relate tokens according to attention, they don't make any assumptions those tokens must represent natural language.

I.e. anything you can tokenize can be wrangled using a transformer, not just language. Thankfully the same author also has a handy example of this: transformer based audio compression https://bellard.org/tsac/