I agree.
What if you are attacked while asleep?
Maybe not as relevant in a home that you can secure properly - though it could be - but in hotels and so on...
In any case I figure that by and large, a flinch is a flinch. Asleep or awake, it is a response that reflects something fundamental about someone's character.
Maybe calling it a "flinch" is imprecise. What the people in the video was doing was not strictly a flinch was it? A flinch in my opinion is the reflexive and mostly involuntary IMMEDIATE and SHORT protective action the body initiates when shocked. If eye-blinking is anything to go by, it is possible to condition most of this reflex away.
But if it is or isn't you should still have full capacity to attack AFTER the split-second of flinching if it happens. Sort of like startling a bear and having it immediately return the favor. It's not like the bear goes "eeeeek" running in circles around in the room.
The people in the video flinched, and kept going in the direction of fearful avoidance. Only attacking because they were cornered.
A response that reflects something fundamental about someone's character...
There are people who would immediately start beating the hell out of whatever woke them like that. From something about their character. Cultivating that sounds like a good idea. But conditioning a new reflex when startled like that should work.
Working it in by sheer drilling.
Lay down, relax - REALLY relax - have a partner with a pad "wake" you, and immediately attack.
I would want a more specific and tactically decisive thing than beating a pad though. Maybe a run through the Beta-8 phases - of course different variations of the drill could focus on different training-goals.
As a side-note; when training, I,e hitting bags. I've often fucked up or if playing, run out of stuff to do. Common to these situations, there is an immediate feeling of confusion. When noticing that, I started to conditioning myself to always do the first and best attack available from whatever position I found myself in at the time. Doubt? BAM!
This sounds like something similar.