Ok, could be that I just missed or misremembered it. I haven't played that actively since April. If this is currently working as intended then this topic can be closed. Would be cool to have an “Allow/Disallow Manual Use” checkbox similar to the ones on Conveyor Loaders/Receptacles on more things like Critter Feeders though.
Dupes will supply buildings with Supplying, Storing and Tidying priority disallowed. At one point even ignoring doors without access permission to get the materials, but I couldn't replicate this after deconstructing and rebuilding the doors.