No it’s not a mistake. This file is in the volume that gets mounted in the container, so it has different paths depending on the point of view, aka inside the container vs outside the container.
This happens when the container is not stopped properly. PostgreSQL needs some time to properly shutdown, and we do that when you stop with our launcher command. However, if your instance if of a big enough size, or there are too many running transactions the database may struggle to stop properly in the deadline it receives.