Originally Posted by
Often1
OP is lucky that Hertz didn't cancel all three. At least two were "impossible" and not made in good faith. It's called preventing inventory spoilage, e.g., the fact that two cars sit unrented on the lot because they are being held for someone who cannot possibly use them.
Airlines do the same thing.
It's quite possible to rent two cars at once. You don't have to tell them about authorized drivers until you show up, and for some classes of them, not at all.