6, 10, 12, 36, and 64 all operate from the same tower cluster in North-West Rehoboth.
28, however, operates from Freetown, MA. So it is in an entirely different direction.
56 is a Boston station that doesn't put a lot of RF down south, especially where you are in Westport.
And the direction will be different enough, even for a slightly directional antenna, to need to reaim for Boston versus Providence, versus 28. (and 69, which is down in Hopkinton, RI)