Keep in mind that in car listening only accounts for between 1/4 and 1/3 of all radio listening. While there are some translators that do pretty well on a good car radio in spite of low power signals, it's entirely possible this translator isn't after the in car listener at all. Given typical listening habits, someone who can't hear a station at home won't listen in the car either. So, maybe they want the at home listener with the translator while 100.7 is adequate in the car?
I didn't spend any real time listening to The Word when I was in Dallas a few months ago, but I seem to remember 100.7 is in mono, which would help it get out a little better than the other Collinsville sticks.