Due to this change by Martin Urbanec while systematizing restriction levels (T230103), plwiki sysops probably can no longer protect pages as editeditorprotected with cascading option on.
Currently, wgRestrictionLevels array for plwiki is [ '', 'autoconfirmed', 'editeditorprotected', 'sysop' ] while that of wgCascadingRestrictionLevels is [ 'editor', 'sysop' ].

I can't actually try protecting one, nor have I even asked any local sysops yet, but theorically and logically speaking, this is not possible.