User Experience begins with You...
Always looking for people to play PzGdr, Napoleonic Games, and Great War at Sea
(the Vassal for GWAS Mediterranean specifically).
You are correct.
A-C has LOS because there is no intervening hex of elevation equal to hex A. Rule 8.42 second bullet.
B-D has LOS because the slope hex at B's elevation is equidistant between the 2 units. Again rule 8.42 second bullet.
B-C is the only instance in your screenshot where LOS is blocked. The line would go through hex 0607, which is closer to the lower elevation unit.