I have very large dogs. Occasionally I am doing something like grabbing them by the collar or sticking my fingers in their mouth, and I have the realization that this dog is Letting Me Do This. If they wanted to, those teeth could break my bones. I've seen these dogs fight to protect their flock and win. I would easily lose if they chose to turn on me.
Yet I don't think twice about prying one of my dog's jaws open to make them take their medication (just eat it when it's in the hot dog, Obi, ffs).
I like to imagine Bruce has regular realizations like this around Clark. He's reaching out and guiding Clark in a direction. He's grabbing a violently angry Clark by the shoulders to tell him to calm down. He's putting himself in Clark's space regularly, touching him, commanding him, arguing with him.
Bruce does something like grab Clark's arm to stop him from chasing after some villain and only afterwards realizes that Clark could have snapped his wrist like a dry twig. Bruce pushes him to sit down when he's injured and Clark just goes, even though Bruce watched him take an entire rocket to the chest without budging not a half-hour ago. Bruce prods at a bleeding gash and Clark just makes an unhappy sound and pouts at him instead of knocking the other man into next Sunday.
Clark lets him do it.
Bruce is allowed the utter audacity to push around one of the most powerful beings on the planet by virtue of pure fondness. He takes it for granted far too often, but once in a while he stops and has a moment of pure clarity where he realizes just how lucky he is.
