Good question. I honestly don't know.
I'm not aware of any policy that says org.wildfly.xxx projects shouldn't deploy directly to Maven Central, and in general I believe doing so is encouraged nowadays. So unless someone knows of any policy against doing that or can think of reasons why there should be, I think it's fine.
All the projects I release are released to
repository.jboss.org. For some that's just habit or just the way the poms are set up with little incentive to change. For others, e.g. WildFly itself, I don't want to eliminate manual steps. For small projects the manual steps bring very little value though.