Transitioning from spotting to belaying

This is some nicely illustrated content about when to transition from spotting to belaying and if spotting and belaying at the same time is possible. It shows how ground fall danger re-occurs in the lower sections of a pitch, climbers' weight differences and what role belay devices play. One point I don't agree with relates to belaying and spotting at the same time. I would only consider this with a GriGri/Birdie and not the other ABD devices. With those, the brake hand should be below the device.

what about when leader is using a stick clip?

and then unclipping first bolt or skipping it so belayer doesn't get jerked up into it? 

Do we really need a video to explain transitioning from spotting to belaying?  Or any kind of instruction.  Really???