It’s the same with the other retailers. They do not own their own factories.
But Amazon Basics doesn't own the factories too - at least not yet.
Same with Trader Joe's
This does happen. Many regional chains do own there own factories however. Many of them produce both store brands and 'premiums brands under license. It's a complicated business.
Same with Trader Joe's store brands, or at least that was the case in the past as I recall reading in The Fearless Flyer.