Trying to get headphones or monitors to sound like a 12" guitar speaker is not possible. Over YT or otherwise. 99% of the time you don't want it to. You can still tell characteristics and comparative insights to familiar amps/cabs/pickups you might know well, so for that it's pretty valuable to cruise YT tone samples. Representative but often badly defined is how I think of video tone tests. It's mostly to just get you into buying the thing or watching the thing, though. It's often the lowest common denominator of content that gets most popular and well funded. Obviously not to be confused with some old head with a nice camera phone running through his 3-4 different devices for an honest and mostly candid comparison. The former being pedestrian, and the latter being utilitarian which I prefer.