The thing is that a shadow Druid doesn’t have any issues killing off a “fellow” Druid that doesn’t agree or take to their extreme tenants.
I think this illustrates the problem of trying to have a computer game as opposed to a human DM manage adherence to a class, as we’ve already seen with the paladin. There are going to be relatively few occasions where simply doing something is going to clearly break any covenants without taking into consideration why. I do very much hope that we’ll get more opportunity to express our motivations in game in the full release as I feel that’s often lacking currently, but I’m not sure it would be enough to allow the game to make uncontroversial decisions about when the player had gone too far. I certainly won’t blame Larian for saving themselves the headache, and reserving their efforts on this front for the class to which oaths are the most important.