Let me ask you a question via a hypothetical, Z. Boy is forbidden from riding his bike for a week. He takes it anyway, and falls off while riding, breaking his arm. That was direct, dangerous, deliberate disobedience. Will spanking him when he gets home from having his arm set and put in a cast serve any purpose?
The answer to that question comes from a further hypothetical. If he hadn't broken his arm, would being spanked for direct disobedience serve any purpose?
I personally believe that direct disobedience requires punishment. It doesn't have to come in the form of a spanking, it could be grounding, restrictions, extra chores, and etc. But to allow direct disobedience to prevail is undermining authority.
In the original hypothetical of a broken arm as possibly being punishment enough. The idea of reaping what you sow, or consequences of actions in the broken arm as penalty of disobedient actions doesn't hold water. It is true that if he hadn't disobeyed, he probably wouldn't have gotten his arm broke, but it in no way is punishment for the original disobedience.
A burglar robs your house, but on his way home he wrecks his car. Should his theft be forgotten because he wrecked his car? Does wrecking his car do anything to change his thieving behavior?
Does the boy breaking his arm do anything to change his disobedient behavior? Or does it tell the boy he needs to learn how to ride his bike better?
I know there is great pain in breaking a bone. I have never broken anything, but I have been around kids who have. The pain is horrible for the short term and then it is replaced by what could be considered hero worship as every kid and many adults want to sign the cast. The broken arm becomes the subject of tales of bravery and honor over time.
There are not many spankings for disobedience that become tales of bravery or honor. Tales of warning maybe. But not something a boy goes to school bragging about.
I am stopping here because I started off into the weeds.
Simple answer to your question. The boy needs to be punished in some way that brings his disobedience into the forefront. He needs to know disobedience is not allowed. To allow his broken arm to erase his disobedience isn't teaching the boy anything, but that with the right circumstances he can get away with anything.
I know this is the way of thinking from the 50's and 60's and not of the new millennia, but I am a child of the 50's.