Lance, in some places the ground transmitters are far enough apart that you might not hear both of them. While that's not usually true at the high altitudes (where NWA was), it's frequently true at the lower altitudes. I often hear center controller call a plane, then call them again on another transmitter (same freq) and ask if that's better or whether they can then be heard.
That's particularly true in some of the places I flew in W. Texas, NM and AZ. It occasionally happens in the mountains in the east.
Again, not usually an issue up high, but does happen down low.