This is very good to know!
I always used the "doesn't work on my system". Though, most of the games I've refunded were really not working on Linux the way I'd like and I just didn't want to hack around or have to reboot into Windows for that game.
They definitely do reject at least some refunds outside the window even if you can get lucky like gp.
They definitely do reject at least some refunds outside the window even if you can get lucky like gp.