I'm not sure, though that sounds like a good guess to me. This is more a question for a general Java forum, since all the Jopr JMX plugin is doing is exposing the Sun-specific ProcessCPUtime attribute of the java.lang:type=OperatingSystem MBean. This is the only docs I could find on this attribute:
Another idea is to see if the source code for com.sun.management.OperatingSystemMXBean tells you anything.
I just assumed somehow that you know what that all means. Apprarently, you are right that I would have had better chances of an answer. After some more googling I have come up with this:
Anyways, thanks for your help