Surcharge Anomaly - confused.

Hi All - I'm a new v-flyer member, but a long standing VS dedicatee and reader of v-flyer. Wondering if anyone can help me understand this anomaly regarding surcharges

A UC return trip to Shanghai comes with this breakdown (excluding fare)

Operating Airline Fuel & Insurance Surcharge YQ GBP 359.00
UK Air Passenger Duty GB GBP 162.00
UK Passenger Service Charge UB GBP 34.49
China International Airport Fee CN GBP 9.00
----------------
Total GBP 564.49

BUT

A return trip to Auckland via Shanghai is this (ie VS to shanghai (UC), then ANZ to AKL (Biz)) - (excluding fare)

Operating Airline Fuel & Insurance Surcharge YQ GBP 275.00
China International Airport Fee CN GBP 18.00
New Zealand Passenger Service Charge KK GBP 14.80
UK Air Passenger Duty GB GBP 184.00
UK Passenger Service Charge UB GBP 34.49
New Zealand Passenger Security Charge IA GBP 4.60
-----------------
Total GBP 530.89


It makes no sense to me as the first flight is a component of the 2 sections of the second. How can the fuel surcharge be higher for half the route?
The cynical side of me says VS are diverting charging from the core fare to the surcharge on routes that you can book with
miles in order to devalue the miles by collecting more cash on those bookings (as you can't book AKL on miles except manually seperately)... but I want to believe there's a better reason. Can anyone help restore my faith?

Fares aren't governed solely by distance travelled, there are competitors and
"what the market will bear" as well involved.

VS also have to make the AKL fare as competitive as possible as they are competing against airlines with more direct options. Whereas with Shanghai its a non stop flight which is a selling point in itself.