Few programs start sifting through the applications as early as September 1st.
However, this is usually a preliminary screening and is done by the coordinator (not the decision maker such as the program director) so rejections if ever sent during this period they are usually about obvious mismatching between your profile and program's requirements such as the visa status or the year of graduation.
Keep in mind, that many programs do not start looking at applications until mid or even late September.
In addition, many programs do not send rejection emails even though they filtered you out. So they don't send you NO and they don't send you YES and that's why the matching process is so stressful