Because the bluetooth audio don't just take microphone input voice for voice commands but takes audio conducted via your skull instead of via the air. Thus the voice must only come from person wearing the FREE BUDS earpieces ONLY. A hacker using the pre-recorded voice of the user played over the air, will not be accepted.
Further more, the front camera on the Huawei phone MUST SEE THE OWNER'S FACE (face recognition) and see his mouth (lips reading) saying the command at the same time. Hence security is very high.
It is used to make electronic payments in these video demos.
No others besides Huawei can do this. All the rest are far behind.