Exactly, that's the real scam with outdoor gear marketing. They slap "universal" on a rainfly or footprint knowing it only works with their own tent models from the last two years. You have to dig into the specs to find the exact compatibility list, it's never actually universal across brands.
But that's just how the industry works. Henry189 is right, universal means within their own lineup. You can't expect a Big Agnes fly to fit a North Face tent, that's not realistic. People should read the fine print before buying anything.