The Java team didn't initiate the process of making it an Internet Engineering Task Force standard; whereas this team did. Even though this is JavaScript centered, it really represents a much broader effort, that should help interoperability between languages and across online systems.

While the IETF might move slower, Java has standards as well. The java-date-time API standardization started in 2007: https://jcp.org/en/jsr/detail?id=310, than a JEP was created in 2012: https://openjdk.org/jeps/150

The point was that language specific standards aren't nearly as important as broad industry standards.