Well, I am a Hongkonger and rented from Hertz in US for multiple occasions over the years.

Whilst I may not be answering the question about CDP issue,
from my experience it is usually easier and probably better to rent directly in Hertz's HK site / hotline.
Say I access the site in HK, the quoted rate is guaranteed and comes
with all sorts of insurance coverage that keeps me protected and worry-free as a tourist driver.

Below is a dummy booking using the HK site,
maybe you can try to use a local CDP and see if it is any better.
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Pickup Time
Sun, 01 Jun, 2014 at 10:00
Return Time
Sat, 07 Jun, 2014 at 10:00

Pickup and Return Location
San Francisco International Airport
Address 780 McDonnell Road
San Francisco, CA US 94128

Discounts PC: 197746

Arrival/Flight Information
No Arrival Information


Your Car
Intermediate 2 or 4 dr., ICAR
Toyota Corolla or similar

Payment Method Pay Later

Discounts Promotional Coupon; : 48.30 USD
for 197746 Promotional Coupon has been deducted from base rental charges applied

Rate Details 1 week at 322.00 USD 322.00 USD
Airport Concession Fee Recovery On Flight Arrivals30.41 USD
TRANSPORTATION AND FACILITIES FEE20.00 USD
California Tourism Commission Assessment7.12 USD
Taxes40.53 USD

Included
Loss Damage Waiver
Liability Insurance Supplement
Personal Accident Insurance / Personal Effects Coverage
Unlimited Free Miles Included

Vehicle Subtotal 371.76 USD
Total Approximate Charge 371.76 USD

Rate is guaranteed.
Taxes, fees and extras, if not included in the Rate, are subject to change.