There may be some more info in the archives of the American Hemerocallis (Daylily) Society. Decades of their Daylily Journal are readable online for members. For example 'Clarence Simon' hybridized by MacMillan won the Stout Silver Medal in 1975 so there probably is an article associated with that. It used to be easy to look stuff up on the members' portal but for some reason lately it doesn't do complete searches any more, but members can ask the Archivist for historical information.
