Pretty sure its because the radial menu locks your aim, while TF2/KF1 classic ZXC/1-9 menu doesnt and it far more accurate, you dont have to aim the cursor at the right spot so your character yells the wrong command because it was one pixel off. Maybe I played games with the classic menu for too long (TF2, KF, Tribes, PVK 2, CS) and I was able to spam voice commands while moving and aiming without problem. Probably Tribes had the best system, although you had to use a lot more keys for it.