The key part of a lounge, that Amex/CO/Chase struggle with, is accessibility. I expect the FL will not have a waitlist or standing room only that most of these third party lounges have regularly. Considering after the allure of a new lounge wears off, especially US based ones, most people aren't showing up significantly early to get into a lounge, and having to wait 20+ minutes is going to send me to the lounge I can access immediately.