i don't think that is giro? that is more like instalment plan... it's not the same I guess?
basically I think the difference in concept is that they cannot be the one who's paying for your car (in this case, the loan is from UOB so they have paid for you to the car retailer) and then use the monthly installment to consider you for bonus interest and pay you the bonus interest. it's a losing business to them
but if it's giro for UOB card, you are paying your credit card bills so they didn't really pay for you in advance (although they did pay the merchant first before charging you at the end of the statement month), so I guess it's the main difference.
I may be wrong lah. but that's my take on the matter.