Because you’re relying on compatibility between older Debian software (systemd, etc) and newer versions installed in the chroot. Things get weird quickly.
Consider a nested privileged container instead (LXC or similar) and cross your fingers that Debian systemd and Arch systemd play nice.
If the above fails just make a VM and pass through the GPU with GVT-g (otherwise pass through the entire GPU.)
If all of that fails install Arch to a USB attached SSD or something.