Kinda been keeping notes for years on this sort of thing and not uncommon for whitetails to carry racks into March, some even into April. Do a search and you’ll see late shedding threads here annually.
Several factors as to the cycle of antlers - genetics, nutrition, age, injury, stress, sexual activity, etc., but drop in testosterone levels is the main factor for shedding. Recently read in a magazine that the testosterone drops causing the skull to reabsorb calcium from the antlers weakening the bone at the pedicle to where they break off.