Hello Chip,
Actually it is not the only place this is configurable, sure of the choices given but potentially they meant different vmk in different PGs - it is also possible to change MTU at the vmk level independent of the vSwitch settings - unfortunately I see it often enough where someone configures it 9000 on the vmk but 1500 on the vswitch (and probably 9000 on the physical switch just to make sure it is as inconsistent as possible ).
Bob