Mining Tower priority

Mining towers should have a generic priority setting (numeric) to balence the behavior with storages. I setup a string of storages connected to a dock with a contract to get rid of excess stone. I set the import priority to 15 on these, with the intent that my trucks would prioritize dumping the rock into one of the several dumping sites I have. Unfortunately this does not occur, and the trucks started filling the containers first, completely ignoring the dump sites. A mining tower priority would force things to use the dump sites first.

I've seen a few similar threads talking about mining tower priority, but it's not clear if they are talking 'per resource' or 'numeric'. If this is a duplicate, feel free to ignore.