That's not what I see reported, they say Haskell tends to have bad memory layout generally and takes a 5x or so hit to performance.
Unoptimised/naive Haskell might be that slow. But that's true of a lot of languages and isn't particularly interesting to me. Java is slow if you do everything the naive way, too.
[0] https://entropicthoughts.com/on-competing-with-c-using-haske...
Java's most badly optimised type, is the String.
Both of them need a string-builder pattern, the default operators don't work around things to do the right thing for you. They expect you to understand how data works.