I should first reply to your post by giving you the definition of "perpetual motion" but some how I think you know this already, and you should know that for this to be what it is claimed to be, it would not be plugged into the wall outlet. (perhaps other than for starting)
What it looks to me is that he has a standard off the shelf motor. and a home built PM generator. the secondary coil windings is large enough to cause the generator to require more horse power than the little squirrel motor can produce. This is what makes it slow down. shorting out the coil only causes it to generate less and therefor the motor will speed up. ( he took the load off of it) As for inducing the generator's back EMF into the drive motor, this is nothing new at all. The Internet is full of much bigger setups than this one. the biggest one that I know of was using a 40kw transformer to do this with,, but the owner is now in jail for investor fraud.
It's kinda simple, if you reduce the output of the generator's secondary Field and feed it's output back into the motor's primary Field,, well sure the motor will go faster. But now there is Little or no work being done by the generator and the motor is still being ran from the wall outlet.
On the up side there may one day be something come of back EMF Field feedback loops. but never will it be perpetual motion.
>with no information on exactly what is observed,
Or in other words,, you don't have a clue what you saw in the video.
>what is unusual, what defies standard logic
Nothing in the video defies anything.
>and with no information on its structure or basically anything else
Or knowlage of an electric motor/gererators
>I just have no idea,
So why did you post a reply to this ?