Raven I expect the desire simply wasn't there. If you're a Heaven Hill or a Beam there's no economic incentive to make special runs for brands that are subsidiary to your own labels. Old Grand Dad was an exception because Beam realized they had a national best seller and it didn't really compete with JBW anyway.
Old Overholt wasn't in enough demand to justify special treatment such as continuing the use of non Beam yeast. There just wasn't that much difference for the average palate to distinguish a flavor shift so Overholt was a throwaway for brand loyalists or those who were shopping merely for price.