AMCAS doesnt start transmitting until July 1st (though some schools have secondaries sent to contact info upon submission to AMCAS)
Most Primary Apps are verified and transmitted mid July thru late August
Most adcoms dont start meeting for review until at least mid-August, more likely September (though adcom staff may be doing early reviews).
Submitting Primary Application June is Early, July Medium, August Late
Having Primary verified and transmitted to school by end of August is normal speed
Having Secondary and all LORs complete to school by end of September is normal speed, by end of October is about late.
Getting primary in early does matter because of all the other items that follow it. But applicants often see the beginning and not understanding how it flows from there.