Do you carry comprehensive/collision? It's in the carrier's best interest to know when you had an incident.
Get in an bad accident today that's not covered under your policy..don't report it.
Get in a minor one tomorrow, then do...make a big claim.
It's clear you just don't know much.
They can use it as a reason to drop you just like your employer can always fire you because you probably used the company internet for personal use once or twice. It's a policy that exists, but depending on carrier, may not be widely enforced.
To the letter of the policy, you should report it. I don't dispute you on that, and I do encourage people to follow the terms of contracts they've signed to cover their own asses. But it is unlikely that he'd be non-renewed for this.
Have you ever looked at the state statutes and DOI regs that govern cancellations and non-renewals? It's quite adequately described as a total mess, and in the policyholder's favor in all but a few states. Such is the regulation of state-mandated adhesion contracts.*
* Does not apply if you live in NH or pay the "self insure" fee in VA.