mongoc_database_command and mongoc_database_command_simple run the command with the client object's read concern and write concern. The spec says the opposite:

If your driver offers a generic RunCommand method on your database object, ReadConcern MUST not be applied automatically to any command. A user wishing to use a ReadConcern in a generic command must supply it manually.

https://github.com/mongodb/specifications/blob/master/source/read-write-concern/read-write-concern.rst#generic-command-method

Same for write concern.