For this case authoritative: true resulted in "EDE: 22 (No Reachable Authority): (OLX2: delegation internal.corp)"
Hmm, right. I'm not sure if delegation works well in that mode so far. Or even whether it's desirable that these explicitly selected auth.servers can delegate arbitrarily by default. But overall the difference is meant to be auth vs. resolver, which is pretty well defined I believe.
(well, with authoritative: false the delegation won't work for sure anyway)