What shows as potential options may vary by location and dates. But usually if they offer the model and if it's booked it will still show up in the list, just as not available.
I searched and Hertz's website still currently shows they have Adrenaline Collection offerings, including the Hendrick Camaro SS (they've retired the ZL1's though):
https://www.hertz.com/rentacar/vehic...e%20Collection