At the last count, Hertz has something like 100 different models on fleet... nad quite a few of these they have in several different trim levels. Unfortunately, given that in many cases you will find Bluetooth is standard on some trims and not others, and even where it is not standard, it may be that Hertz included it in some option package on the car, all of which makes answering your perfectly reasonable question mission completely impossible.

I fear the only solution is going to be check against an individual car when it is allocated to you, and if it does not, then it's quite legit to go back and request a different model (though not perhaps if you have only booked a Group B car - generally the costlier the car the more likely it is to have what you are seeking, of course).