Can't tell if it's sarcasm, but breaking a tempered-glass automotive window is difficult without proper tools. I tried breaking a window at the junk yard a couple years ago and decided that a headrest is just about the last object I'd consider. The foam part of the headrest absorbs a lot of the shock of your strikes. Combined with being inside the car and off-angle to the glass makes it even harder to break.
Even using a crowbar is not as easy as you'd think. I gave it a good swing and it just bounced off the window because I hit it with the flat part of the crowbar. I eventually managed to break a window by striking the glass with the very tip of the long end, but it wasn't easy.
Those orange escape hammers suck for the same reason as using a headrest; being off-angle and needing room to swing makes it hard to break the window from the inside. I'd also be concerned about being too badly hurt after a crash to swing effectively.
The best tool I tried was the resqme. It's spring-loaded, so there's no need to swing anything off-angle. Just press against the window. I have no affiliation or interest in the resqme. In fact, I wish I knew about them sooner. I think I read somewhere that they've been around for 10 years or so and that the tool was originally only for sale to first responders.
Yes, it was sarcasm, but it was based upon my experience of being in 2 serious car crashes. I vividly remember being a passenger in a head on collision and watching as the front hood folded back across the shattered windshield and blocked our view of the outside world. The driver and I, while not seriously injured, suffered forward whiplash trauma to the head, neck and chest from being held in by the seatbelts. But, more importantly, we were in shock. We just sat there, not fully cognizant of the degree of damage, or what to do about it. Fortunately, a police car was nearby and talked us through the extrication process. I very much doubt that the person posting this bit of clickbait was ever involved in a serious accident. This solution, aside from being nearly physically impossible, completely overlooks the shock and trauma and the focused attention that would be required to implement it. It has often been my short coming to deal with stupidity with sarcasm. Right or wrong, it was my view of this proposed simplistic solution.
I cannot remove the head restraint in my preferred driving position, so this little tid bit is of no use to me. However, there may be occasions where there is a requirement to break glass or puncture something in an emergency, and this little piece of light hearted humour may be enough to jog your memory if and when that situation arises. I've now reclassified my yearning for toasted marshmallows as an emergency situation.
I have four of the Life Hammer Evolution located either on or near all four passenger doors. It would just be my luck to get trapped in the boot.....