Lots of technical choices are made based on cool-factor, not technical or business merit, especially in startups. Go is often a perfectly reasonable choice... but is often chosen for the wrong reasons.
So translated into objective facts that statement is just "Go is cooler than Java."
At DockerCon EU a couple years ago someone who worked in VC firm mentioned that every startup they were talking to was choosing Go. Go is better than Python in some cases, better than Java in others... but in many cases you could just use Python or just use Java and it'd be just fine. Often Python is better (much more libraries) or Java is better (much more libraries, and has generics unlike Go's "let's reinvent all of Java 1.0's faults" design).
But Python and Java aren't trendy.