Mesos configuration flags are one-way and aren't expanded to their corresponding MESOS_ENV variable.
The MESOS_LAUNCHER_DIR however, is necessary here:
when the executor needs to resolve the path to run, for example, health-checks.
Instead of the passed-in argument argv (which contains the Agent's --work_dir instead) is the path that ends up being used.
How can the requisite MESOS_LAUNCHER_DIR env var be available when docker/executor.cpp (a child process of mesos-slave) attempts to read it?
The relevant email thread is here: