The PMDG 747-400M is a special case, since it's a Combi airplane so, it's not flagged as a Cargo plane, but it has a Main Cargo door. So, in order to prevent the cargo main ULD loader to interfere with passengers boarding, it will arrive after the passengers.
This is generally true for every airplane configuration that result in loaders on the left side of the airplane: they will wait for the passenger bus to go away before arriving.