Hi Barry, this is classified as a pistol because it has a pistol brace. The Trinity Force Breach Blade Pistol Stabilizing Brace included is allowed because it is not a stock. Without the brace, it would still be a pistol. You can add a pistol brace to pistol.
A stock is different from a pistol brace, and if you added a stock, then you would have a short barreled rifle and be subject to registration and a $200 tax stamp.
Hope this helps clear this up for you. Stay safe & have a great day!

it is a pistol not a SBR because it has a pistol brace not a stock A pistol brace is different from a stock. While both are designed to provide support and stability for firearms, a pistol brace is specifically designed to be attached to a pistol, allowing for improved control and accuracy, while a stock is designed for use with a rifle. A brace typically has a shorter length of pull than a stock and is made of rubber, plastic, or metal The main component that differentiates an SBR from a braced pistol is a buttstock

Hi Barry and welcome. The rear attachment is a Brace and not Stock which retains the classification as a standard Pistol/Handgun. Cheers, stay safe and enjoy!