This is mostly because people wrongly assume that LLMs can count things. Just because it looks like it can, doesn't mean it is.

Try to get your favourite LLM to read the time from a clock face. It'll fail ridiculously most of the time, and come up with all kinds of wonky reasons for the failures.

It can code things that it's seen the logic for before. That's not the same as counting. That's outputing what it's previously seen as proper code (and even then it often fails. Probably 'cos there's a lot of crap code out there)