You're right. On two counts. My folks live in a small town in Western NY and everyone has the same exchange. I have to believe that's a minority of people by the numbers, but I could easily be wrong, and if rural towns are specifically your target market, it wouldn't matter if I was right...
And I worked for a call center company once, which employed a similar technique. Not down to the exchange, but by area code. We ran the numbers and found that we were much more likely to reach a person if we called through a number that belonged to their own area code, people don't pick up for out-of-state callers.
We were calling for customer satisfaction surveys, on behalf of companies they had done some business with – and almost always with a presence in their local area. So it wasn't technically a deception, unless you think that area codes should reliably represent the caller's location, in which case you'd be fighting a losing battle to be sure...
In hindsight it may have helped us work contact lists faster but it did nothing for our survey completion rates. People who were not likely to answer an out-of-state call were apparently also not likely to answer a survey, even once you got them on the phone. To us, that trade-off was still worth it, because we were usually contracted to try each contact on our list either 3-5 times or until we reached a person who (completed or) declined the survey or asked you to stop calling.
If you didn't want the calls, then we straight did not want you to continue getting them. Another rule we had was, it should not be possible for the person's phone to ring, and when they pick up it's just dead air. That means no predictive autodialers. (And of course that was the first rule to change when the company was sold, barf.)
We also ran the numbers on each area code and did a little cost-benefit deciding whether to buy those numbers or not, based on how many times we'd use them. If we didn't own a local number, we didn't use one. And we made sure that if anyone called back, the first thing they reached was a robot with a single digit to push to be added to Do Not Call list.
Turns out if you make it easy for people to get the calls to stop, you get a lot less angry people calling the reception and less angry voicemail messages, which makes for better call center employee experiences and better outcomes all-around. (I guess another strategy is to just spoof Caller ID with a number you don't own, so they can never call you back, and run the predictive rates so high that you never actually talk to an employee either. Totally unethical and it has to stop!)
The number of calls I receive which immediately hang up seconds after I pick up is absolutely ridiculous. I just imagine this call center full of people with auto-dialers going on full-speed across the room, nobody is wearing a headset and nobody is at their desk, but everyone is just sitting around a cash bonfire telling stories and laughing...