US medical schools have rolling admissions. What that means is that they being interviewing and accepting people before the application deadline. Let's say that a school has an application deadline of December 1, but they begin interviewing in July and accepting in October. Let's also assume they interview 250 applicants and accept 100. In July, they might interview 50 students. In August, they will interview another 50 or so. By the end of October, they may have already interviewed 200 applicants and accepted 20 of them. If you apply at the end of October, there are now only 50 interviews and 80 acceptances left. Why would you apply late when you could have applied earlier and had a shot at 1/250 interviews or 1/100 acceptances. These dates and numbers are not realistic and totally made up, but it does show how applying late in the cycle is a bad idea.

If you can't submit your application until September, it won't get verified until October. By the time you complete secondaries, many schools will have already interviewed and accepted students. You should wait until next cycle to apply unless you can submit your application much sooner than September. It would be better to apply in May 2022 and be really early!