Confirmed — this is a plain bug, not missing content. Grendel is registered as the Magician job instructor, and the code that handles job instructors answers you about advancement and then stops dead; it never gets as far as checking whether he has any quests. He actually has 23 quests attached to him, three of which a level 12 Magician can take right now: Beginner Magician's First Training Session, Defeat Faust, and Who Broke the Seal of Marbas?. The same hole hits all five instructors — Dances with Balrog, Athena Pierce, the Dark Lord and Kyrin are equally silent about their quests.

The fix is to run the instructors through the same shared quest menu the shopkeepers, refiners and ticket sellers already use, so "talk about my training" becomes one row of the list instead of swallowing the whole conversation.

Fix shipped — this is now on develop and will be in the next build.

The diagnosis is in the comment above; this is just to confirm the change is written, type-checked, built and pushed rather than only planned. Please re-test when the next build goes up and reopen if it is still wrong.