If it occurred to me, the 'big deal' would be:
* What's the 'hold' for? Customer does not have use of Hertz asset and is not a 'credit risk'. No reason whatsoever for a hold. Would anyone be OK with a hold placed, say, a month ahead of rental? Two weeks? Same for hotels, or anyone. Restaurants? "Credit hold applied as soon as you book."
I can see your point here, A month would probably be annoying...but wasn't it only 4 days? I don't think that is unreasonable, personally.
* Appears that the OP was not informed that the charge would be levied in advance - even if its just a 'hold', it affects the credit available on your card. In the OP case OP was informed by bank of a 'significant charge' (or hold) the OP was unaware of. OP may have been embarrassed in another establishment if further credit was declined because of lack of credit available.
* What happens if the rental doesn't take place? How much hassle is there to get the 'hold' un-held? My understanding is that hire car companies deliberately don't usually take cc details as a 'guarantee', like hotels do, as they don't want to be bound to supply the booked car - they want flexibility to substitute another car, like we know they do all to often. Now they appear to want it both ways. Not sure why the OP had their cc details known by Hertz- maybe they are a club member and like me with AVIS, they have cc on file.
My message to the car company would be: Hertz, or anyone, keep your grubby hands off my credit until there's a good reason for them to touch it, not before, and certainly not until you tell me.
Hmmm ... I'll just make sure the cc on my Avis file is an expired one. Let them try to take a 'hold' out of that!
I totally get it, I guess I just take the approach of 'don't sweat the small stuff'.
Each to their own!