Canon t5 video face focus?

I'm a vlogger, i used to use a nikon l820. I upgraded and have a t5, when I put it on face detection in video it puts a box around my face and is ready for me to half press the shutter to focus. My question is, if it can already find my face can't it focus by itself so I don't have to keep holding the shutter? And if not what canon slrs can do this function? I know the 70d can, but what else?

I can this as good feature if you're changing focusing distances a lot. However, if you're not changing focusing distance, then just set the camera to MF, focus once, and forgheddaboutit.