If you are an affiliate and are paid to send traffic to another site or a distributor, you must identify yourself as an affiliate or a distributor in your ad text.
This is rather vague. Personally, I send traffic to some of my sites which are a combination of content and affiliate links, and have never added 'aff' to the ad, and have never been questioned about it.
I could see this being a one of those 'depends on the uniqueness' of the content to how G enforces this policy.
After all, how many sites actually sell their own products or even hold the products they sell in their own warehouses?
Tons of big commerce sites don't take posession of many of the products they sell & then you have shopping engines and on and on.