I work at Culture Amp and have been involved in hiring decisions, including for people who were excited about Elm so happy to comment here. As others have guessed, this is an "indication" not a "rule", and it was more about people who were applying _only_ because of the tech stack, rather than a sense of wanting to build a quality product, or alignment to the company's mission (improving workplace cultures). We hired plenty of people who mentioned Elm. I mentioned Elm in my interview.
Part of the reason for this is very pragmatic: during the time when Elm was in common use at Culture Amp, almost all of the APIs that Elm would have been talking to were written in Ruby on Rails, and our engineers were expected to be able to contribute to work that required changes in both the Elm front end and the Rails API. If someone was a functional language purist, and only wanted to work in say Haskell on the backend... then they wouldn't enjoy being on one of our product teams where writing Ruby on Rails code was part of the day-to-day.
Part of the reason for this is very pragmatic: during the time when Elm was in common use at Culture Amp, almost all of the APIs that Elm would have been talking to were written in Ruby on Rails, and our engineers were expected to be able to contribute to work that required changes in both the Elm front end and the Rails API. If someone was a functional language purist, and only wanted to work in say Haskell on the backend... then they wouldn't enjoy being on one of our product teams where writing Ruby on Rails code was part of the day-to-day.