I don't think all kids go through this stage (reading backwards, upside down etc.) but probably a subset of self-taught early readers do. It's probably part of the package of their code-cracking and visual-spatial abilities. I would think that a child who learns to read when taught through some process is less likely to do this, even if the read sooner than their peers, or the type of kid who might not read early, but once they learn they really advance quickly past their peers. But I think those kids just learn it differently.
I only have the one kid and she did this. The other cousins are bright but haven't done this (older) and show no signs of heading that way (younger). None of them have any interest in puzzles, building, or mechanics at all. There is probably some link there somewhere.
I love the toast story. My DD went through a stage when she was about 3 1/2 or so where she tried to nibble as many letter shapes as she possibly could out of little twist pretzels. It was totally hysterical.
