...Moopsy!...

Looks new to me. If I had to guess it's whoever picked up Badgey making their move.

Wouldn't prime!Chekov be like 12 around this time frame?

It does though. As the others said, Scotty did have to jury-rig some modifications for long-term storage and even then he wasn't able to save the other survivor long-term.

Star Trek had a long history of taking cues from capital-T Theater, so a musical was kind of a logical extension of that.

And the DIS s1 klingons look broadly like the TNG klingons, just exaggerated.

Then as someone who does know a lot about this stuff I can tell you that you are making a lot of assumptions that are not the case.

...That's literally what happens in the Dune books.

I mean... not that much. Daleks have gone through three redesigns just since the show went back. Sontarans went from the world's most unconvincing rubber masks to makeup. And how many eyes do Silurians have-- two, or three?

because apparently Star Trek, unlike every other fantasy and science fiction thing I like, is Forbidden from being treated like a secondary world that should have its own internal consistency.

Nonsense-- other long-running universes encounter retcons and visual redesigns all the time. Quick, how old was Dick Grayson when he first became Robin? What color is Superman's S? How old was Magneto during the Holocaust? What happened to Luke's father? Did James Bond fight in World War 2, or participate the Cold War?

Perhaps it implied that.

But it only ever implied that, and meanwhile we had other evidence that implied a separate conclusion, in the form of Kor, Kang, and Koloth.

Which is more likely-- that every Klingon Kirk encountered during his five-year mission was a survivor of the augment virus (edit: Including Kahless, who lived and died centuries before Archer!) and no Klingon encountered outside of that time period was; or that the Klingons ruthlessly quarantined or even executed carriers of the augment virus and wiped it out before it got too far, and TOS's visuals aren't literal?

I dug 'em. It was a good experiment in pushing Trek's aliens beyond a forehead and an accent.