Are brands considered their own manufacturer?

When looking up different products on Amazon and scrolling to the “manufacturer” section, I see that almost every brand registers themselves as the manufacturer. I doubt most brands are actually doing their own manufacturing in house….does Amazon not check when registering for brand approval or making a new listing? Or are they technically the manufacturer? I’m particularly interested in gated categories, as that’s where I plan to sell. I know from an insurance point of view, private labelers are considered their own manufacturer, but they don’t do the manufacturing themselves. Thanks!