I tend to agree - this video was quite confusing, and I've been working on / designing / repairing electronics for 25 years now.
The video isn't so much "wrong" in what it says or demonstrates, but it completely threw me off, because of the term "voltage doubling".
It's not really a "voltage doubler" circuit in any real sense, and there will only ever 5 Volts across the LCD segment(s) at any given time.
This and me second-guessing myself for about half an hour. lol
I thought I'd missed something over the years, and had to test it for myself...
https://imgur.com/a/Wm0tHSure enough, yes, the o'scope will show 10 Volts P-P across the NOT gate, but that's only PEAK-TO-PEAK, which means that the only reason the o'scope appears to show the apparent doubling of the voltage is due to where it's reference point is set at "0V".
Plus, obviously the 'scope is designed to show negative voltages that swing below that 0V reference level, and that's what you would see when the signal across the NOT gate switches polarity.
I don't think the video explained clearly that there is not a "real" doubling of the voltage, as the signal only goes positive and negative with respect to the reference point on the 'scope, and doesn't actually create twice the voltage across the LCD (or any other load) in the circuit itself.
Granted, it was partly my own brain fart as well, but it appears that lots of people on the video comments are very confused by this too.
I even had to grab a cup of coffee and bacon sandwich before I finally realised that my original assumption was correct. lol
Quote from the vid at 1:21 (not gigawatts, sadly)...
"We do actually get 10 Volts peak-to-peak ACROSS this LCD for a 5-Volt supply. So it is actually really voltage doubling..."
I think statements like the one above are what's causing most of the confusion (and the video title).
Yes, the P-P voltage is effectively doubled, but the "voltage doubling" phrase makes it sound like there would be a true 10 Volts across the LCD segment.
OzOnE.