The Dragonlance guess was always weak, based on flimsy logic, the races and subclasses were vaguely Dragon themed, that's it, but none of it actually resembled anything in Dragonlance, the Dragonborn races were very different from Draconians for example.
On the other hand the Spelljammer UA was NOT vague, it's was blatantly Spelljammer. Uniquely Spelljammer races, that don't appear in any other setting (except FR, and rarely then, but still it's FR, even a MtG creature ended up in FR LMFAO, it's the borg of settings), with the possible exception of the Astral Elf which I'm pretty sure was intended for a different book and the Thrikreen, which could be Spelljammer, but just as like could have been snuck in for Darksun later on.
Like it's not even a question as far as I'm concerned about Spelljammer in 2022.
And Star Fromtiers isn't even D&D.