If running in a containerized environment ENV is injected only to the container, at container runtime. If you’re running your containers with a single process, you are doing the exact access control you just outlined. At that point what is the difference between a file on disk with read permissions for the proc owner vs only the proc having the ENV injected to its shell at runtime? I’d maybe even say the ENV at runtime is more secure than the chown’d file on disk because the ENV injected variant is ephemeral and when that container/proc dies, so does the ENV sitting in its memory, whereas the other leaves a file on disk potentially depending on where it was written to, regardless of who can access it. Then there’s the fact that a lot more people than you think run containers as root so all file access control goes out the window.

From a security perspective it is always more secure to have something only in memory of the running process than it is to have a file on disk regardless of file permissions