Or to be more specific, they changed the name of Athasspace to Doomspace at the last minute. From what I understand, the Doomspace we got was basically what they had been planning to do with Athas in the book. The fact that with a simple name change it might easily have flown under a lot of radars that it was ever intended to be a take on Dark Sun speaks volumes IMO.
I don't think it would have flown under radars, personally.
Rather I think people noticing would have been delayed until after the book actually came out, rather than people noticing
before the book even came out, because there were significant specific clues to connect it to Dark Sun, and then people would have talked about it a ton. But I think your point is that it was such a questionable take on Dark Sun that it was hard to read as Dark Sun without the name, and if so I agree.
I have no idea what they thought they were playing at, honestly. Were they seriously thinking "Oh let's destroy Beloved Setting (TM) Dark Sun in an adventure for Much-Less-Beloved Setting (TM) Spelljammer, that will definitely go well for us and make D&D fans happy with us!"? Because it genuinely seems like they were, and how out-of-touch do you have to be to think that? I mean, very significantly out-of-touch, I'd say - not just with ENworld (who cares about us, honestly), but with people who like D&D in general. Sure, some proportion of people have never even heard of Dark Sun, but equally that means this does nothing positive for them, and if they do find out about DS, they're unlikely to see this as a good thing! And for anyone who likes Dark Sun, at all, this is insulting and awful. So the only people who would be pleased by this are some tiny subsection of D&D players who like Spelljammer and wanted to see Dark Sun destroyed! That's what, like 20 people on the planet? I guess most of them working for WotC!