I too would like to know what's going on in their mind. Given they're apparently under the impression there that the most notable contender in that space is Go. Scala isn't a bad call though, and is JVM. Java itself seems like a non-starter for doing actual data science due to its verbosity and lack of scripting.

Instead, Julia should really be first to mind when considering that question. Although I might expect the author to respond with something about the mysteries of 'production'.