Kristoffer O
This info may be very useful in many cases. If you know that the province contains some worthless site you may consider not attacking the castle especially if it is well defended. OTOH if you know that reward is great you will aim for it.
However, I don't think it is a bug. I like thinking it is a feature .
If it was a feature you should simply be able to click on that magic site instead of going around like that. So something should be changed, one way or another.
This issue has been sitting in the shortlist for a long, long while, as the item "BHV Nation Overview & Scouting Reports", but has gotten no answer before now.