So when the article says "But the real finds involved lost scenes that were filmed but never released," I'm thinking that this "filmed but not released" scene was from The Wrath of Khan, not from "Space Seed." I think someone simply misunderstood--either Mr. Ingram or T'Bonz. (Maybe the unused scene was unused in both productions--but I think it's probably referring to just TWOK.)
That makes sense. You're probably right.