There's a reason why adaptive sync should work only on full screen is because Windows and in turn the software focuses on one thing so the monitor knows what refresh rate to change to. Performance in the single digits when in windowed mode in one driver patch and then the next patch full screen is broken.
It went back and forth to which was more broken when they did it. From what I've read/seen their attempts to do it in windowed mode have been a buggy mess.