Draw-back - if you float the aircraft and don't have your hand on the throttle, it may start adding N1 to keep target speed as you coast 2 feet above the runway.
Actually, nope. It will go into retard flare mode at 27ft but not add thrust in that stage of the landing process. We do use this method from the classics on and it worked well so far, however you have to know how it behaves if you come close to the lower speed limit and on capturing altitudes, otherwise you will be caught by surprise. Oh, and we still do add the wind additives for manual thrust and even that way in gusty weather the low speed protection will sometimes engage as it isn't apparently triggered only by going below bug speed but by trend as well.
Besides, if you are flying in ARM-mode not having your hand on the thrust levers is not really good airmanship anyway as it is basicly manual thrust except for low speed protection.