What we refer to as browtines by all official scoring systems are nothing more than tine 1 or what most call G1. The fact this deer or deer like this don't have the typical G1 is moot, it is still the first tine closest to the base or pedicle of the main beam. Long n short this deer is typical. Non-typical is abnormal growth, pretty much anything that grows not in a straight up fashion(Split tines, multiple tins growth off 1 G base position, drop tine, kickers, etc) can be officially classified Non-typical but also uniquely NT's can be scored as a typical just the abnormal growth is a deduction of the final typical score. In a case where a heavy typical framed deer has a few 1" stickers it would be more adventageous to score him typical with the few abnormalities as deductions vs NT. A good place to find out what is NT vs Typical is the Boone & Crockett or Pope and Young websites, they both have information about classification, scoring and even score sheets to score your deer that will calculate for you.

Genetics, age, food, water and stress level all have effects on year to year antler growth. Why a deer does or does not have browtines, I would say it is mostly to do with genetics or age.