And yes, I too think that parent-first is more natural, but the weirdness here is that "plain default" is false while adding classloading config turns it automatically into true.
Well, the "plain default" knows about deployment type:
* ear --> isolation --> look locally first == parent-first=false
* war, which has parent-first=false by default
Whereas jb-cl-domain.xml is deployment type agnostic, hence uses the more natural default.