Can you share what the cost was so I can complain to someone at Hertz? I think it's reasonable if they charge for fast charging the vehicle upon return, but it shouldn't be extortionate. Should be what a fast DC charge would be (~$15-$25) so they can cover equipment and energy costs to quick turnaround the vehicle for the next renter.
One of the benefits of EVs is that electricity is somewhat ubiquitous (including airport rental facility parking garages), so it's not great UX when an auto rental company is incentivizing customers to chase down fast charging at the last minute before return vs just topping cars up when returned.