...then the client actually calls the ccaround.jsp layout- and within this arranges the whatever-page as ROW(PAGEBEAN)INCLUDE.
So the client's data requests (== the normal client roundtrips to your applicaiton) are going through this page. If you switch your browser to development mode then you see one "ccaround.jsp..."-POST communicaation per serer roundtrip.
If your application runs into some error which is passed to the client, then the ccaround.jsp-roundtrip is the one to get the 500-response.