I think we can presume the reason that between usually refers the space between things, less the things. “The ATM is in the lobby between the elevators and the restaurant” probably mean the ATM in the restaurant.
The ATM is in the lobby between the elevators and the restaurant” probably mean the ATM in the restaurant.
This starts with "The ATM is in the lobby", so there's no reason to think it's in the restaurant. The "between the elevators and the restaurant" gives you a clue that if you go to the lobby and see either the elevators or the restaurant, but not both, keep going until you see the other one and once you do see the other one, you've passed where the ATM is.
This is kind of a bad example for if between means a closed or open interval, however, since neither the elevators nor the restaurant are non-occupying boundaries, but rather places that could be occupied by an ATM. However, if the ATM is found at the elevators or in the restaurant, you wouldn't describe the location of the ATM relative to both of these, you'd describe the location as at/inside one of them. You might say, though, that the ATM is at the elevators, (with the elevators being) {near,after,before} the restaurant, to explain where the elevators are.