Debian JRE Package Bug

In attempting to install openjdk on Debian I ran into the following error:

Setting up openjdk-17-jre-headless:amd64 (17.0.13+11-2~deb12u1) ...
the java command requires a mounted proc fs (/proc).

The /proc directory exists and is populated, so why does this error occur?

The postinstall script ends up here:

/var/lib/dpkg/info/openjdk-17-jre-headless\:amd64.postinst

It calls mountpoint to test for /proc:

    if ! mountpoint -q /proc; then
       echo >&2 "the java command requires a mounted proc fs (/proc)."
       exit 1
    fi

Why the maintainers chose to check for a /proc with mountpoint I don’t know. I am working inside a chroot environment with the mount created on the outside. On the inside it looks like an ordinary directory. So the test fails.

When I avoid that test, the program installs and runs as expected. So absent some other consideration that presently escapes me, the test is wrong.