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.
I can shed a little more light here, having been an IU student then. Indianapolis was on ET during Standard Time months and CT during Daylight Savings months. As a result, basically WTHR followed the network from 10-3 local time (except for noon news). So when MGHS aired at 2 local time (actually 2:30, IIRC), they carried it. At 3 local time, they didn’t.
And the week she taped aired the week before the 500, so the booking was timely.