Read the thread that FrancisV shows a link for in post #4 abv., in particular posts #38 & 41 if you want part of my take on the question. I’m still waiting for someone to post the applicable code sections and figures, since I don’t have a copy of the 2009 IRC.
BigMac.... certainly the type of loading influences the lateral loads on the deck. Wind loading involves wind pressures positive and negative, a function of wind speed, on projected surface areas; and its resultant acts at the centroid of the projected areas. It is basically treated as a short duration static load at that centroid. Earthquake forces act on the mass of the deck, at the center of mass of the deck, and may act in any direction, in a very dynamic fashion. While floods would act on any projected area of the structure exposed to the onrushing water’s force. All of these can act in most any direction and at some point, or in a line of action, some distance removed from the ledger or other attachment to the house. Thus, they will cause shearing forces in the plane of the ledger or wall of the house; but in addition, since their resultant acts at a centroid point removed from the house, they will also cause a moment, a twisting force couple, trying to wrench the deck diaphragm away from the house. There will be a tension force at one corner of the deck and a compression force at the other corner, the moment couple, due to this twisting action. And, since we don’t know which direction the force may come from, either corner can be the tension corner. I suspect the 1500# and the hardware are intended to counteract the above. IF they are needed.
Maybe with the next edition of the IRC they can come out with an additional 600 or 800 page volume which defines exactly when these things should be considered and when they are needed; depending on the day of the week, the sky color, local altitude, siding color, and such like.