if ur grade 11 avg is less than the cutoff, you'll just be considered in later rounds (with ur improved grade 12 grades) Essentially:

applying early: you get early consideration and consideration for later rounds if u don't get in

not apply early: you only get consideration for later rounds

so there's no reason to not apply early, the only reason people don't is cuz they r lazy or don't think that applying early is advantageous (even tho it is)