Process requires redirection

I have a simple script that runs Steam in the background using tmux. Steam automatically downloads their bootstrap files that I am not allowed to redistribute otherwise. When trying to migrate this background task from Xorg to Wayland, it would silently fail in with the new xwfb-run. I am using Arch Linux (fully updated), Weston as the compositor, and the latest version of xwayland-run from git is installed.

Xorg (works):

tmux new-session -d -s steam 'xvfb-run --auto-servernum steam'

Wayland (workaround):

tmux new-session -d -s steam 'xwfb-run steam &> /tmp/steam.log'

Expected Wayland behavior is that this should work as a drop-in replacement with no redirection of standard output or error:

tmux new-session -d -s steam 'xwfb-run steam'

I only observe this behavior when using tmux. However, the legacy xvfb-run tool has no issues with this scenario.