As far as I can tell, no one said resumable exeptions are only possible in Haskell. That would be pretty silly, as they didn't even originate there. In fact, they indicated it probably would be possible-but-awkward in Java. What was stated was that it wasn't possible in Go, and that seems to be correct, and have nothing to do with Haskell's choice to return (Either a b) where it's appropriate instead of (a, b).
It's certainly the case that whatever you wanted to use resumable exceptions for is very probably plenty possible in Go. But no one denied that. It's also possible to implement a language that's like Go but has resumable exceptions, either in Go or by modifying the Go compiler, but not only is that a huge project (which may permit "entirely impossible" as hyperbole) but the result is quite arguably not even Go anymore.
It's certainly the case that whatever you wanted to use resumable exceptions for is very probably plenty possible in Go. But no one denied that. It's also possible to implement a language that's like Go but has resumable exceptions, either in Go or by modifying the Go compiler, but not only is that a huge project (which may permit "entirely impossible" as hyperbole) but the result is quite arguably not even Go anymore.