By using the word "almost" with regards 2 + 2 = 4, you have not exactly dispelled LLM "nonsense".
A human (with a modicum of maths knowledge) will know that 2 + 2 = 4 (pure integers - a fact by assertion). A maths worrier will get slightly uncomfortable about 2.0 + 2.0 = 4.0 unless they are ensured that decimal places and accuracy are the same thing and a few other things.
A LLM will almost certainly "know" something that is certain, if its training set is conclusive about that. However, it does not know why and if enough of the training set is suitably ambiguous then it (LLM) will drift off course and seem to spout bollocks - "hallucinate".