The thing is, Cotton Candy was also a G3.5 McDonald's pony and sold in the retro sets and recently had Christmas ornament released that named her. Perhaps Hasbro learned their lesson not to assume anything.
I think Tales was intended for the European and particularly United Kingdom audience. The fact there is a king and queen, Starlight wore a judge's wig in Stand by Me, and soccer was the game of the day seem more geared towards the U.K. audience. Though, Soccer was trying to penetrate the U.S. market in the 90's as a fledgling professional soccer league was in existence for a short time. We had the Detroit Neon.
Whatever the case, Tales aired the summer before those characters hit the shelves...in Europe and the brand disappeared everywhere else. They might have been Hasbro of Europe's idea. It was a simple set with all earth ponies and no gimmicks. It might even been an attempt to relaunch the brand similar to Transformers Generation 2. It would be interesting to pick the brains of people responsible for these decisions.
Getting back to G4, I liked how the Season 5 premier didn't glorify the Mane 6 and their friendship. In fact, they had to rely on others to save them. FiM has so exalted the Mane 6 it probably makes other ponies seem inferior in the eyes of the children watching.