Yes, I think about this everytime people mention Celestia being the "first alicorn" in MLP. The Pony Tales cartoon was released after the Glowing Magic Ponies and Rockin' Beat Ponies were already in the shops, so they altered them for the cartoon rather than vice versa. As the Ponyland of MLP Tales was portrayed as an "ordinary" place with no magic, the Glowing Magic ponies were the only ponies allowed to appear as anything other than Earth Ponies...as they were "magical ponies from across the rainbow" (as quoted from the UK Tales annual). Hence, Tunefull lost her horn when she appeared in the cartoon!
I always wish Tales hadn't been released so close to the end of the G1 line. There was so much potential for the series and a lot of good toys (Lancer, Teddy, Ace, Miss Hackney, the Schoolbus and Ice Cream Parlour, for instance) could have come out of it. Instead, even the main characters never got released in the states, the G1 toy line ended, the cartoon got cancelled after just one season, and they didn't bother to release anything more than the seven girls for the European market. Very, very sad.