> people who've only used languages with 'and' and 'or' will only take a few minutes to get up to speed

No. Cognitive overhead. You pay for it every time you parse these words in your brain. You pay for it by reducing the number of nested/combined clauses that you can parse on the fly.

(This is far from the only readability issue with Go, by the way, and you're right in that it's among the more superficial ones. The language is designed so well in all ways except the one that matters the most, it hurts.)