I think the confusion comes in because of a disconnect on what is meant by "trust" in this context. It's not that, "I would trust this person with my life," or "I would trust this person to not to rug-pull me." Rather, it's simply, "I trust that this npub will continue posting notes that I will be interested in seeing." And as soon as they prove that trust to be misplaced, you 86 them from your follow list so you no longer see their notes.