if your definition requires universal observer agreement you already have that issue with special relativity / light cones / the spacetime metric.
many worlds posits a single universal quantum state it's just only partially accessible to observers, which is different from saying that it simply doesn't objectively exist.
The problem is that this is not only about Haskell's fundamentals. It's about them being extended with backpack, an extension that very few people use.
And honestly, I don't see the point there either. I know that backpack is meant to solve some problem everybody has, but I haven't been able to fully understand what that problem is. Specifically on this article, I don't see the gain over using a type class.
But taking this the other way around : it's also interesting that some cosmologies are known to be incorrect, because they would enable alternative forms of consciousness.
Actually, we're already past the peak of star formation in the universe. So the universe is well on its way winding down.. less and less stars are being created.
We're seeing the universe more middle aged than especially young
many worlds posits a single universal quantum state it's just only partially accessible to observers, which is different from saying that it simply doesn't objectively exist.
maybe it depends on your definition of objective