Not sure if this is a bug or requirement - though SCI JDOC does not mention anything that would justify same SCI class to execute more than once( neither does it deny it).

Depending on AS version ServletContainerInitializers are handled bit differently( 7.x adds WsSci by default if jboss-web.xml has boolean flag for instance ), however all version allow to spawn SCI via jar services mechanism. Trick is that there is check on what and how is spawned. It is possible to spawn the same SCI twice and both will have a go. In case SCI does not behave or depends on servletContext.xxx methods return value, this can either make AS misbehave or throw NPE(from SCI) or other nasty exception. Example [1]

[1] https://issues.jboss.org/browse/JBWEB-298