OP I dont know if what I ran into at times was the same with your rental. But many times when Im getting quotes (even with Costco) when I change the time of p/u it will spit out a different rate sometimes cheaper sometimes more expensive
So much so that Ive booked the way cheaper rate and cxed my flights booked within 24, and booked a different flight to correspond to when I will be picking up the booked car, if theres a large down time before I can get the car
So it is possible ( not probable) that there was a more expensive rate for a p/u B4 9 .
My Budget last weekend I p/ued up 1/2 hour early since there was a 29 min grace that I needed for the d/o. My contact was for $20 more since it was charging me according to my d/o time I reserved. Returned the car with 20 mins of the grace period used and my final receipt was for my original rate w/o the extra hour having been charged. Although if I wasnt in a rush I would have had them change my return time to mirror the exact time I p/ued the car to be safe