AIUI the thin build is meant to be the same as the fat dist except the jars are not in the modules; rather their gavs are in the various module.xml and JBoss Modules finds them in a maven repo.
But currently the differences are more than that. For sure the org.jboss.as.product module isn't even present in the thin build. This will lead to test failures in EAP as new tests added in WF 13 will not work if the console module location info from the product module is not available.
Comparing the galleon provisioning plugin config from dist/pom.xml to build/pom.xml gives a sense of the problem.
Note that this diff is not due to the switch to galleon. The fact that a different galleon config was needed for build vs dist is because that is what was necessary to match what the prevacy legacy build created.
This work should make sure servlet-build is correct as well.