That is just not a solid argument. There are countless examples of LLMs splitting "blueberry" into "b l u e b e r r y", which would contain one token per letter. And then they still manage to get it wrong.

Your argument is based on a flawed assumption, that they can't see letters. If they didn't they wouldn't be able to spell the word out. But they do. And when they do get one token per letter, they still miscount.