Andor's Trail

It seems like a bug rather than a deliberate design choice that
Was there some reasoning behind it, or is it just an oversight that was never fixed in the code? If it is deliberate, then

This is not the only quest that has "Disallowed Substance" as a prerequisite.
Just complete the disallowed substance quest. It is a core quest that really needs to be completed

That's fair, but maybe a little dialogue nudging would help new users (without actually changing the game flow). Right now, it seems totally disconnected.

Well, one thing that makes this case different is that getting the bandage for Fanamor is on a timer, so if you take too long she dies.