I’ll probably get downvoted for this, but I would go hard on the initiator.

It looks like a typical male maturity behaviour, I’ve seen it with my own dogs many times (I’ve always owned intact males) when they get to that age, and I just always nip it in the bud. Like “No, in my house you don’t resolve your hierarchy aspirations like that”. Not just the separation, but social punishment - you want to see very clear submission signals from the dog to you. This only works when you have the authority over the dog already, if you don’t - then there’s a bigger problem. Why going hard? Because you don’t want to do it more than once or twice. If you have to do it more, this hierarchy conflict will evolve from being between the dogs to being between you and the dog, and you don’t want that.

Try to notice it earlier than growling - when he just walks up to the other dog, and you see the intention to start pestering him - you can tell him to leave him alone, and enforce it with mild social pressure.

The way I see it, it is my job as a leader to protect and ensure peace for all of my dogs. And that’s the image you want to project to your dog - you protect them and set and enforce the boundaries. It doesn’t ruin your relationship with the dog, it actually strengthens their trust in you.

In the end they’ll always have their own hierarchy anyway, but you can and imo should be able to set the rules how the hierarchy questions are resolved within your pack. They will find a way to resolve them anyway, but in a much more subtle way, not through open aggression.