These things happen. TMP featured extensive and elaborate alien makeup and costumes. Didn't see much of it at all. Far background crowd at SF HQ and then again a crowd scene on the Rec Deck. A few standout characters but nothing representative of the array of aliens they worked on. A lot of effort for comparatively little screen time.
The ultimate example is STXI's Rura Penthe scenes, which featured dozens
of elaborate aliens (including new-look Klingons, a Gorn, a Salt Vampire and a freaky guy with three faces) only to be left on the cutting room floor.
At least the new look Klingons are being reused in the next movie.
There was a Salt Vampire in Rura Penthe? In the eleventh
Salt Vampires went extinct in "The Man Trap."
well we don't see the fourth side, or perhaps there is a ladder from another deck.
Maybe it's the creepy guy who terrorized William Shatner in that Twilight Zone episode.