In interviews with Roddenberry and Fred Phillips (makeup man on TOS and TMP), it was mentioned that it was only the then-recent development of slip latex, and foam latex, that enabled the style of crest used on the Klingons in TMP (and the ridged foreheads of TMP's Andorians). Prior to that, makeup appliances had to be baked overnight in an oven, and they were rarely able to be used more than once.
It's not that Roddenberry imagined TOS Klingons as always having a crest. The availability of new techniques, and the crested alien developed for either "Planet Earth" or "Genesis II", inspired Roddenberry to challenge Fred Phillips to make TMP's Klingons "more alien". That was his only brief.
What's changed? "Star Trek Enterprise" showed us crested Klingons, and then a Season Four two-parter which explained how some - not all - Klingons developed flat human-like foreheads.
The makeup tests for the ST XI's Klingons are hardly too removed from the nose appliances used on Worf in TNG and DS9. We're not meant to know what's under the helmets. Even the makeup man didn't know!
You know, if the ST XI makeup guy had replicated previous Klingon makeups, you (or others) would be saying, "They already changed everything else, why didn't they take the opportunity to change the Klingons?"
Put Kor, Kang and Koloth, and the Excalbian recreation of Kahless the Unforgettable, side by side. They don't look very much like each othe, even though the main variation is colour of makeup. Then add to the mix a TMP Klingon, Kruge, Maltz, Torg, ST IV's Kamarag, ST VI's Colonel Worf, Chang and TNG's Worf. Klingon faces and sulls have as much variety in them as human clines.
