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Looked at video and should say the private key you generated via shaking a disposable cup is not random but rather pseudorandom in fact is the coin in the cup has the limits in all directions. IMHO, you would get the better results with flipping the coin up by the snap of two fingers.
Thank you for your feedback. Probably you are right.
There are different ways of flipping the coin -
https://www.wikihow.com/Flip-a-CoinAnd iI beleive that every human flipping a coin makes it in some pseudorandom way because of his habits, physical conditions, etc. And in fact, all these different singularities would add the additional entropy for the key generation process (like one man will make the flips with 51%/49% odds, another with 48%/52% odds, etc