My wife and I use to go to the Smoky Mountains a few times every year , when we go we try to always spend at least one day at Cades Cove . I have seen several bucks there still wearing their headgear many different times in April.
In my experience when a buck sheds his antlers is based on how hard his body was taxed during the rut. It's not uncommon to see young bucks hard horned into April, they generally aren't allowed to rut hard. Also, it's not uncommon to see mature bucks that rutted hard drop in late December. Deer have personalities like people. Most want to breed but a rare few get to old to care or was never interested.
Thought they were all shed at my place. Grabbed a chip this afternoon while checking for mushrooms. 8 pt still packing both sides at 11 this morning. 2 bucks he was with had a bit of velvet up maybe an inch