This is such a strange article. It starts out describing how Haskell was well-suited to their problem (or at least tries to) and then suddenly says:

The thing is: Biilmann no longer uses Haskell. It’s not entirely practical. Not enough people know how to use it, and this is unlikely to change. “Haskell is like a programming language from an alternate future that is never going to happen,” he says. “It solves all these problems it promises to solve. But it’s so different that there is no chance it will become common.”