Can't confirm because I'm not playing games with Linux.
Anyway I can confirm that pressing and keeping pressed the LEFT SHIFT key for at least 2 seconds, the glitch seems to disappear for a short period of time (minutes) and the spurious EV_MSC events stops.
I used evtest utility to monitor live events from /dev/event/input3
Can't confirm because I'm not playing games with Linux.
Anyway I can confirm that pressing and keeping pressed the LEFT SHIFT key for at least 2 seconds, the glitch seems to disappear for a short period of time (minutes) and the spurious EV_MSC events stops.
I used evtest utility to monitor live events from /dev/event/input3