I haven't tried the Java 7 support yet but WTP is the one providing the Java Facets thus my first guess is Web Tools limitation (which i'm surprised they put in/didn't fix if true ;(
You can check if its Web tools or jboss tools by creating a utility jar project without any jboss tools facets/features.
If you can't then its web tools and open bug at http://bugs.eclipse.org, if you can then blame us and open bug on https://jira.jboss.org/jira/browse/JBIDE
In any case share the link here if you get around to it - in any case i'll raise it on the WTP call this week to hear what the status is (assuming its webtools ;)