Puppy manners is a phrase that gets thrown around a lot.
Just because you have taught your puppy “sit” does not mean that you will have a well behaved dog. However if you to teach your puppy to “sit” until I tell you to do something else, then you are teaching something much more valuable.
I teaches your puppy that whatever you suggest the puppy do next is a rewarded activity and it also teaches your puppy to wait for your next suggestion for his activity.
Those are the underpinnings for teaching impulse control and make it easier for the dog to resist “temptations”. The rewards for resisting are higher than giving in.