Also, This guy https://www.youtube.com/watch?v=ZR3Jirqk6W8 had his Haskell startup bought by Facebook. I expect it was because they wanted the technology he invented, and him as well.

While Haxl is great and is a good example of Haskell usage in the industry, it's not a good example of the usage of formal methods, since functional programming is only the first of the two steps mentioned in the article.

The title of this post made me hope they were looking to hire a "proof engineer", but alas, they're only explaining how to become one. It's already hard enough trying to find a Haskell job, finding one in Isabelle or Agda must be near impossible!