Thanks for your comments, I've found the book and read it once more, here is what he really wrote, for the question "Will I ever marry?"
"Regardless of what signifies whom, an applying Sun/Moon conjunction is an excellent indicator of marriage."
So, now I am wandering is it applicable to all relationship questions, or just this kind of questions?
Hi - Depending on a person's culture, "marriage" often means the querent is thinking about a long term relationship. If your querent has specified this in discussion while settling on the horary question, then "marriage" and a long, term, serious relationship can mean the same thing. It depends on what the querent has told you, the astrologer.
Frawley would never advocate that you take a sentence like the one you quoted as something to be followed blindly - in fact, in the sentence just above the one you've quoted, he says "But do use your common sense: ..."
Also, he had just been writing about timing in relation to the type of question that begins "Will I ever ...?" He was making the point that if you've got the applying aspect, then you'll be able to find the timing "in the chart somewhere."
One such aspect could, in fact, be an applying Moon to Sun.
What Frawley has written is not wrong but perfectly reasonable.___