Explanation
This split catches people out constantly. A video that ran organically without incident can be rejected the moment it is put behind ad spend, because ad policy is stricter on claims, on synthetic media disclosure and on regulated categories.
The rules that move fastest are the ones about AI content. Anything you read about them more than a few months ago should be re-checked before it is relied on, which is why every claim about them on this site carries a date.
The common mistake
Assuming an organic hit will work as an ad. Check the ad policy separately before spending, because the rejection usually arrives after the budget has been allocated.