This is my understanding of it as well. While the bug is still bad due to the fact that a JVM instance will connect to the attacker's endpoint, any JVM above 8u121 wouldn't execute the code with Java's default configuration.

It's also mentioned as part of the release notes for 8u121: https://www.oracle.com/java/technologies/javase/8u121-relnot...

Edit: Looking deeper into it; the JDK version used within the POC's GitHub, from the screenshot in that repo, is 8u20, released in 2014.