There's
PDI = pre delivery [to the customer] inspection.
Always charged to the customer. Usually under the dealer
ruse of ensuring the vehicle is washed and gassed up, all bolts tightened, paper work etc...
and then there's...
PDI = post delivery inspection.
Paid to the dealer in some form or another by the manufacturer upon delivery of each vehicle to the dealer by the manufacturer. Why? Because this is the last point of quality control the manufacturer has before a vehicle is delivered to the customer. The manufacturer depends on the dealer for the servicing and to make sure the vehicle is defect free. The PDI fee is supposed to cover the dealers employee cost for time for the "inspection". Now often built into the MSRP so the customer may not see it as such.
The PDI scam was created by the dealer long ago to find a way to get paid twice for what should be a cost bourn by the manufacturer, not by the customer.
It's not unusual for the "PDI" costs to be the first $$ a dealer will "knock off the price" for the customer. After all, the manufacturer has this covered anyway.
So back to the theory of why Honda might be shorting the dealer on drive oil. Well, anythings possible, however the question remains: Is Honda willing to risk their reputation on a relatively small savings? Or, possibly they are depending on the dealer, after all they are paying the dealer PDI.