Humans are REALLY bad at reading what’s happening with dogs. We ignore really bad stuff and we stop, even punish, perfectly normal behavior
...But then at some point, say at twelve or sixteen weeks, even earlier for the quick maturers, the little soft fuzzy schnookums-wookums becomes a growing dog, and her little games start to involve using her teeth in a real and deliberate way. And instead of bumbling into the adult dogs’ heads and falling over, she’s lying in wait and then barreling over and jumping on their heads.
The adult dogs decide they’ve had enough, and they begin to punish her for this rude behavior. If she jumps on them they roar, they knock her with their mouths, they send her ki-yi-yi-ing into the next room. When she has play interactions with them they don’t hold back anymore; they pin her and knock her over and she yelps and rolls away.
The human says “Oh no! Poor Gladys! They’re being rough with her!” and they begin to supervise the play. Every time the adult dogs get “rough” they are stopped or disciplined. If they continue to “victimize” the puppy they are totally separated; she plays alone and they play alone.
...THIS IS SUCH A BAD IDEA.
Puppies learn from adult dogs. A vital and absolutely incontrovertible role of a healthy adult dog is to teach the puppy how to be a good and polite dog. The adult teaches–yes, by physical punishment, though that punishment is not cruel–how to interact with other dogs, how to live in a pack, how to ask permission, how to back off, etc. If you stop that from happening, not only does the puppy grow up with SERIOUS issues that will hurt her chances of being a normal dog who can get along with other dogs, you build resentment between the two dogs. If the adult dog is never allowed to complete a lesson, he will try harder and sooner the next time. If he’s stopped again and again, pretty soon he will decide that the only way to deal with this is to remove the puppy from the picture entirely.