Not sure why you would think that using both hands simultaneously defend and attack is a Wing Chun only ability.
Because I didn't say using both hands simultaneously to defend and attack...
I said both arms in VT have dual functions. That is a single arm can defend and attack in one beat. Using two such arms in rotation allows for a sustained onslaught with automatic protections. Two dual-functioning arms are in effect like four. Much faster and safer, but to do this we need to have squared facing because it requires the use of elbows, and it can't be done when turned sideways where one arm is back.