I can't say with 100% certainty but I don't think our brains turn words into numbers and perform math calculations equations to make images. It's a bit of a cop out saying "we don't know how the brain works". If you apply the same analogy to ChatGPT we don't use math calculations to write words. If anything GPUs are not using shortcut, they use brute computation, to get to what our brains perceive as similar.