The L8 manager of our org declared that all projects must be on the JVM, and if the language wasn't Java, then we would need to submit a six pager explaining why. Perhaps he was just being conservative, but to me there's something off-putting when those types of decisions come from managers rather than from the engineers.
That said, our org did manage to have a few projects that aren't Java, so I guess I would have to concede that the Java claim is factually false as well. But it sure doesn't feel like I am empowered to choose something other than Java.