Yeah, the Vancouver station already makes WOAI hard to hear on 1200.
I'm a geography geek in addition to a radio geek (I was the kid studying map books for hours on end instead of doing my homework 35 years ago), so I like being precise. However, you make a good argument here. It's not like shortwave, where you're trying to say you "heard" South Korea if you are listening to the WHRI relay of KBS. In the case of mediumwave, the transmitters are usually 20 miles or fewer from the cities of license. Actually, in my case, the transmitters for both KQWB and KMOX are actually farther away from me than their cities of license.
With that in mind, I'm going to rethink how I categorize locations. I'll admit that being able to add two more states to my loggings just by listing my stations differently is tempting!