Answer
The logical printer still needs a PHYSICAL mapping entry in the Print Agent's configuration file pointing at some real print queue on the server, even if that queue doesn't actually print anything — a local, do-nothing print queue defined on the Print Agent host works fine as that target. Without a PHYSICAL mapping to something the Print Agent can recognize as an actual printer, jobs sent to that logical printer stall instead of completing, even though the report/archive side of the job works correctly.