Doug Drexler answered the question. When Datin built the 11 footer he painted the left side to match the right in terms of markings and windows. But he didn’t make the model truly symmetrical because he did not add all the same physical details as the right side. Apparently the intent was always to focus primarily on the right side. It was a cost saving measure because more detail meant more time involved equals more money. In this state the model could be photographed from a distance and pass muster on a smallish television of the era. Of course today you couldn’t get away with that with today’s large screens and high resolution. Today the model would have to be finished all around.
When changes were made to the model for WNMHGB the biggest issue was adding internal lighting. For them to do it meant obliterating the incomplete left side with exposed wiring. This left only the Starfleet pennant on the port nacelle (which is still there) and the pennant on the secondary hull (as can be seen in the photo Doug supplied).
When the model was modified again for the series the only thing that remained on the left side was the pennant on the port nacelle.
One can try to split hairs to say “finished” and “completed” don’t mean the same thing. But bottom line is when Datin completed building the model and delivered it the job was finished…for the time being. But the model itself was not finished in the sense of being fully symmetrical on both sides because it lacked physical details on the left side.
The video’s author is reaching for a gotcha moment believing he’s discovered something everyone else has apparently missed somehow. But those in the know and involved restoring the model know it was never fully finished on the left side, certainly not in the sense the video is suggesting.
The intent of the model, by utilizing reverse decals (done maybe once or twice), was always meant to represent it as being symmetrical. I suspect, though, that if there had been sufficient time and money, and lighting had been planned for from the onset, the model could have been fully finished all around. If
Star Trek had been a feature film it could have been done that way. Certainly for TMP the refit model was fully finished all around and smaller as well.
But it didn’t happen that way and here we are.
Interesting to note while TOS used the right side of the ship in TMP we mostly see the left side of the model, almost as if to say, “Folks, we’re giving you something never seen before in the series.”
