LOL! That's why I said, "usually."
AC Delco advertises the Advantage line as genuine AC Delco parts at a more affordable price point. They are made by a variety of suppliers around the world who can make the part cheaper. As to whether this matters is probably best decided on a part-by-part basis. I have no experience with ball joints, but I do with brakes, shocks, sway bar bushings and end links, and outer tie rods. I decided to go with the outer tie rods made by Raybestos for the AC Delco professional line instead of the slightly cheaper Moog parts, but if I did it again, I would have no problem going with the Moogs. As far as sway bar bushings are concerned, AC Delco Professional, NAPA and Moog are the same part, made in the same factory and just relabelled. (NAPA doesn't make their own parts either.) I am pretty picky about my parts. We don't have an AutoZone in Canada, and I am somewhat glad. Their cheap discount line of parts is the cheapest ones they could get someone to knock off in China, and their "premium" durmast parts are often on par with the cheaper line of NAPA.
I also know the lifetime warranty scam. It started in the brake industry many years ago - advertise brakes with a "lifetime warranty" and then sell them the cheapest brakes you can manufacture. This guarantees that 80% of the clients pay way too much for cheap brakes and never come back, and 20% keep coming back every few years for their "free" lifetime brakes, and then get sold on the overpriced accessory parts and overpriced labour.
One of the things I love about forums such as this one is people sharing information about what parts are worth the extra cost and what parts aren't. I use only NAPA Ultra Premium brake rotors and NAPA Adaptive One brake pads, Timken bearings, AC Delco electrical parks and spark plugs and Moog (or higher) suspension pieces.