Edit: I’m glad so many of you have had no issues with multiple monitors. My set up is a little unusual (3rd display is an infrequently used large tv hooked through the receiver) and is definitely solveable but will take some effort (and honestly, I’d rather spend my spare time outside or with friends, so who knows when I’ll fix it.)
While humans cannot see 144hz explicitly, persistence of vision does not work like a monitor. Your vision DOES see differences. You can still notice how ‘smooth’ motion is at higher frame rates, etc.
That said, framerate isn’t the only stat that improves visual quality. Even wholly outside of color reproduction, having a monitor that supports blanking between frames (frame1, black, frame2, black, etc) can make even the same FPS ‘feel’ smoother and reduce ghosting and other effects from the panel.
Also, there is a BIG advantage of fast panels for variable refresh rates. Even if your game can never run past 60fps, a panel that can push updates very fast generally has a far greater ability to hit the rendered framerate, ‘feels’ more responsive at the same framerate, and often has a greater range of FPS they can support. Basically… there are many good reasons FreeSync has multiple tiers.
So basically… good job falling for ignorant dogma!