1) My understanding is that the source of this story is Kathryn Leigh Scott, who is not an infallible source. The story is so widespread, however, that there may be other sources that I don't know about.
I've only seen the story in KLS' My Scrapbook Memories or attributed to that book. And you're right that it's hardly an infallible source.
I just wish that KLS would have made a distinction between what might have happened during rehearsal and actual taping because some of the things she writes about [spoiler](like the incident with Terry Crawford supposedly bouncing up off of the mattress during Beth's fall from Widows' Hill)[/spoiler] certainly never happened on camera. And what's extremely unfortunate is that countless articles have picked up on anecdotes like that as though they actually did happen on camera and made it to air - and far too many have used them to deliberately make DS look ridiculous. Though, of course, if KLS actually thought that incident did indeed happen on camera and made it to air (like she supposedly did with the incident involving David Ford and the falling teleprompter), well...