Yes, why would you need to replicate those values in jboss.xml..?
It's my understanding that the value in the ejb-jar.xml file is optional (i.e. a default value) that may be changed by the deployer. What I was (incorrectly) assuming was that JBoss established a separation of responsbilities between the bean developer and the assembler/deployer inherent in the different deployment descriptors. For instance, the bean developer creates the ejb-jar.xml file exposing it's configuration properties, and the assembler and/or deployer creates a jboss.xml file for the particular deployment.
Somewhere in the EJB spec it talks about the possibility that the assembler may not be able to modify the ejb-jar.xml file, although I personally don't have this problem.
Other tags in JBoss/EJB (e.g. resource-ref) follow this model of declaration in ejb-jar.xml and assignment in jboss.xml out of necessity because the EJB spec does not provide a way for the bean developer to supply a value in ejb-jar.xml. So, I expected the same pattern for env-entry-value, but now I understand.