The woman who said it was Harnick's daughter. (I think) I never heard that quote before, but I was not surprised. When I think of what Sondheim liked in lyrics, Harnick's songs tick off most if not all the boxes: establish character, move the plot along, have a beginning middle and end, etc.
Sondheim said he'd never critique a living lyricist. I wonder if he wrote anything about Harnick to be published after his death.
Ashman is another one I'd've loved to hear his opinion on.