By this point the model has been updated. A flush occurs as EJB3 automatically flushes the PC at method boundaries, you can turn this off by using a flushMode=MANUAL conversation.
been away from seam for a while but previously I always used "em.merge( .. )" when handling objects in Conversations. Has something changed in seam in regarding to Transactions/Conversations (maybe the Homes are using Extended-PCs or something else I have not used yet?)
A home uses an SMPC (which is like an EJB3 EXTENDED PC but for the scope of the conversation which means your entities don't become detached during the conversation) so there is no need to merge.