ITT: We create a hoax that claims the Vanilluxe line was going to be in Red and Blue.

Let's think of explainations first. Here's one:
According to Bulbapedia, Nintendo of America had ideas to localize the designs of the original Pokémon. The Japanese side of Nintendo convinced them not to localize the designs though. (this is totally legit) The Vanilluxe line is one of the localized designs that was going to be put into the game, but was left out because of time.