What does any of this have to do with the requirement to have a GES at each structure?
I?m am not sure where you are seeing a reference from article 550 to article 250 or 250.32 requiring a grounding electrode connected to the mobile home equipment grounding system at the mobile home distribution panel When supplied by a feeder.
How are you getting from article 550 to article 250?
Article 550 specifically indicates the connection to the grounding electrode at the outside adjacent service rated disconnect. I do see a requirement for the GEC to the service equipment when installed on or in a manufactured home.
The requirement has more restrictive verbiage requiring the grounding electrode conductor a means of routing it outside the manufactured home. It seems to be implying that the grounding electrode conductor needs some insurance not to be in contact with the structure after making connection to the service equipment grounded conductor.
Granted there is no given reason for the routing language but when you couple that with the insulated equipment ground, I tend to conclude they are trying to avoid either stray voltages or some other cause that would elevate a voltage on the grounding system in manufactured home.