I don't think that is correct. When each provider negotiated a rate with a station the coverage area is one of the things that affects the rte. This could be a mistake or there may be an odd coverage pattern here. we do not know.
I'm not one of those affected by the zip code shutout, but I find it hard to believe that MASN would have settled for something less than the same viewing area as CSN has.
BTW, I received a non-responsive response to my email. I've emailed back asking that my message be forwarded above the CSR level.