I have to go with Quinn. Two years ago, I applied for prelim IM and EM. I was "late", and I got almost nothing. I did get one interview before 1 November for prelim.
It's only common sense: all others being equal, the app that's there is better than the one that isn't. The program director that says the only one who sees the apps are the secretaries underestimates the secretaries.
IM programs look at over 2000 or 3000 apps per cycle - for one person, that's enough to make your eyes bleed. If you want to be one of the thousands that may be inexplicably good, but stuck in the morass of apps, and, therefore, missed in the dark night, as the PD just can't take anymore, you do so at your own peril.
And if you do wait until after 1 November, you're fine if you have 500's on your boards, AOA, and research, because the bar gets higher, and, also, as Quinn said, don't be surprised if all the spots are filled. Believe me, a painful email is "we want to interview you, but all our spots are now filled. If someone drops, we will notify you."