When he returned the car he got an emailed receipt showing he was charged “the full dollar amount of the rental.” When he called customer service he faced “several long holds” but was finally told he was charged because he “did not select the right vehicle type at SFO.”
In other words, he used his point for a standard vehicle. Hertz didn’t have that car, so the points couldn’t be used. Hertz did him a favor by renting him anything at all, but demanded cash for that rental. Only they never told the customer this was happening and that his award reservation wasn’t valid.