From what I've heard, QWERTY wasn't designed to slow typists down, but rather to try to stop commonly adjacent letters being adjacent on the keyboard.
I think a glance at the top row is enough to disprove that -- qw/wq and yu/uy are the only uncommon two-letter combos, while extremely common ones like we, er/re, rt/tr, io/oi, and ty are present. There are even several common three letter combinations -- wer, tre, ert, rty, and poi. If you expand to include vertically adjacent keys, you'll find even more.
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