Bind mounts not visible in chroot

Question

I am using a debootstrap envs on my Arch system. I bind-mount some directories from my home dir into the chroot fs home dir, ie. /home/user/foo → /stretch/home/user/foo. I can see the content from the host Arch system in both places, but from within the chroot environment when logged in as user, the foo dir is just empty.

Edit: I should not that the same setup used to work, but for some reason now doesn't. I'm not aware of any relevant configuration having changed.

How is this possible?