You're right of course - it could be a Sway issue, but with Sway being engineered from the ground up to be a Wayland compositor, and conforming to that design, I would still blame Wayland.
To give a comparison: NTFS has many annoying flaws and limitations, but because it's ultimately a file system created for the NT kernel on Windows, I blame Windows for its limitations.
Besides common sense would suggest that usually when it comes to launching games a display protocol would have more impact than a choice of WM, though Wayland blurs that line because of it's unusual architecture compared to what we know and love with the X11 protocol and good old Xorg..