If you go outside as soon as you come out of the arrivals hall and turn left, you'll pass the bus shelters and hang a right under the covered walkway at the eastern end of the international terminal. Follow it to the car rental building. Do your business and walk out the other end of the building to the cars.
I've probably never used Hertz at Turnhouse so I can't say their desk is actually in the building with the others. Also, which might add to the confusion, is that's there's a small, temporary-looking building as you walk into the lot. It might darn well have a Hertz sign on it, but I've never noticed people doing business there - - which means absolutely nothing. But, that little building is right next to the gate that everybody has to drive out.
When I google-mapped what you did, the Hertz teardrop was right on the little building. Other agencies were scattered for a mile where there's no lots and no desks. The entire rental lot was completely empty when I switched to satellite view. The imagery date was this year. The last time I was there was right about Thanksgiving.
It makes no sense unless there was a complete change in the last few months and I haven't noticed significant construction in four trips last year. The existing rental building was pristine (and has the last bathroom stop - - on the right as you go out the back door).
Actually, I've never been to Turnhouse - - I just dig crap up on the internet, so that's why it might not make sense. But, if you need to sleep there for an early departure and don't want to get stiffed for a hotel bill, the moveable chairs next to the window as you come out of arrivals are the only ones that are comfortable.
Back to Nero - - they have the best expresso in the UK. The Costa place as you come out of arrivals sucks.