Andor's Trail

I don't know if this is intended behaviour.
I did destined for great things. It is completed, in the completed quests tab. When I talked with Erethori, it updated.

Normally it's not intended, but it can happen that you do some things for a quest later, after completion.
In such cases we don't want to lose these steps, so these are just added afterwards.

There were many different quests where this can happen. It's no big deal. You've just encountered a scenario where you found a quest step that is optional for the progression of the quest after you've completed it