https://doc-stage.usersys.redhat.com/documentation/en-us/red_hat_jboss_enterprise_application_platform/7.1.beta/html-single/migration_guide/#running_the_server_migration_tool

We should warn user that migration tool creates a new configuration from the source server rather than a composition of source and target server configuration - all changes on target server made between installation and running the migrate tool will be lost.

See e.g. JBEAP-12078 for more details on this - example with mgmt users.