Not sure of your source, but all of the Indianapolis-area newspapers on Newspapers.com have MGHS listed for 2 p.m. Central on WTHR that month.
That comes from me misreading a TV listings grid that looked like 30 minutes of Match Game followed by Star Trek. By May, they WERE airing it, you're right, but for a time, they weren't. Muncie Star-Press on October 30, 1983 prints a short blurb about the show's debut, wrapping up by noting that WTHR will not be airing the series. By March 7, I'm still not seeing the show at all in the grid--their afternoon schedule that day is News, Search, DOOL, Another World, You Asked for It, Gilligan's Island.
On April 25, the schedule reads News, DOOL, Another World, Gilligan's Island, Star Trek.
So going back to what Scott initially said, this actually looks more and more like it was a gesture of goodwill because WTHR finally agreed to start airing the show.
EDIT: Just saw that Matt suggested the same theory while I was typing it up. Hat tip.