Everything I've seen, including two of the colouring & activity books, indicates that Spin-Out was a red version of the Sunstreaker toy with the name and bio change at some point late in the game.
It's this history that makes me want to buy this, but Sunstreaker (in any colour) is an expensive MP. And I thought buying Blue Bluestreak was pricey.
When you think about it the unused names like Spin-Out, Blow-Out, Sprint, Guzzler all names seem odd today but Sunstreaker, Cliffjumper, Windcharger and Trailbreaker would seem odd if we hadn't heard them for 36 years.