In fairness, making one of TOS' Klingons look human involved a shave and staying out of the sun for a few weeks.There is precedent for that. Arne Darvin was a human looking Klingon in season 2 of the original series and the Enterprise crew couldn't tell he was Klingon until the tribble inspired McCoy to investigate further with his tricorder. And it makes sense that after Tyler, Starfleet developed better ways of identifying human looking Klingons.