I have a question.

Where are people getting the idea that any head bump is likely a concussion?

A bump or goose egg on the head is not indicative of a concussion. Tenderness or soreness on the head does not indicate a concussion.

Other than amnesia of the event and a bit of time before or after, a person cannot self-diagnose memory dysfunction. That requires sophisticated tests. Self-diagnosis will likely lead to all kinds of erroneous conclusions.

If one had no symptoms of a concussion at the moment of the impact, why do so many worry so much about the impact being a concussion? You can't back up time and erase the head bump. What would change if it was a minor concussion with no lingering symptoms?

When one suffers a concussion, you treat the symptoms, not the impact.