/proc/pid/stack permission denied to root in container

I am using the latest Bookworm Debian Docker image.

In a full Debian VM, I can su -c "cat /proc/<pid>/stack" for a given <pid>. However, the container (which is root by default ofc) throws Permission denied. Starting the Docker container with sudo makes no difference. Using su in the container also makes no difference.

Why can’t I access stack files in a container? Is there an alternative path to the same info?