In case other jobs are already in hand, it may be worthwhile to be a little more open and share the same with potential interviewer.
It helps both ways - you may land a better offer; the prospective employer knows in advance that you may or may not accept. Downside being the prospective employer may be reactive and may not extend any offer.
I strongly agree with the author that professionalism helps in the long run even if you decline the offer.
