At a high level, sure, everything you say is true. As you get closer to the ground, maybe not so much. Yes, you should not recommend that your students skimp on studying for the MCAT, participating in meaningful ECs, or going to class and studying for exams so that they can pre-write secondaries years in advance. Does this mean that it should not be made a priority to make the time to do it so that they don't have to crank out maybe 100-150 essays in the space of a few short weeks, under pressure to push them out the door, once the cycle has begun? If someone is focused and serious, I can think of very little more productive in the months leading up to a cycle than to put yourself in a position where the only secondaries you have to worry about are the ones that changed from last year. But that's just me.
Totally agree on the hyper-focus on being early. It also amuses me that every year, in every school specific thread, as soon as anything happens (secondaries, IIs, decisions, etc.) everyone needs to know when everyone interviewed, submitted, was complete, etc., as though the process was linear, when they see, every year, in every thread, that there is no pattern as to when things happen because applications are always triaged and stratified, as disclosed by every adcom on SDN who ever answered the question.
Finally, correlation was not meant to be strict. It was actually kind of sarcastic. Adcoms say most people don't pre-write, so it's not necessary, while also saying most applicants are not successful, but not following that by saying there is consequently no reason to apply. Of course I never meant to imply that most participants on SDN are successful (there is ample evidence to the contrary) or that most everyone else is unsuccessful (I'd have no way to know that, beyond the fact that 57% of everyone is unsuccessful). No logical leap was made or meant to be implied.