Merging wrapper arguments in Docker

out of curiosity, why is the 8.3 external modules folder different in docs vs .ignition-jvm-args?

my compose command:

    command: >
      --
      -Dignition.projects.scanFrequency=5

but found in .ignition-jvm-args.<8 random chars>:
-Dignition.gateway.externalModulesFolder=data/var/ignition/modl

docs: