It's a boolean option: if enabled the coredump processing on the host would forward the coredumps to the unit's code. The idea is that a container manager enables this on the container's unit, and this magically ensures that coredumps that happen inside the container are delivered to the container itself, and are then processed inside of it, with the container's own coredumping logic.
Security-wise this is really nice behaviour I think: to a large degree coredump handling inside…