I was trying to compare the contents of these two installers:
jbdevstudio-product-universal-7.0.0.GA-v20130717-1700-B362.jar
jbdevstudio-product-universal-7.0.0.GA-v20130720-0044-B364.jar

The only expected difference was in central. But in fact there were many differences in these two plugins:
org.jboss.netty_3.2.5.Final-20130531-2315.jar
com.ning.async-http-client_1.6.5.20130531-2315.jar

I could provide instructions on how to run the comparison using the dist-diff tool that is able to spot differences in classes. But for now let's start with the probable cause.
In build B364, both of these plugins had this additional file in them:
eclipse.inf

with this content:
#Processed using Jarprocessor
pack200.conditioned = true

Now the question is: Why was the option used in B364, but not B362?
And what are the consequences, if any?