My understanding is that MCAS altered fight characteristics not only to match older 737s and avoid additional pilot training. MCAS altered fight characteristics so the FAA would approve the MAX as a commercial aircraft period. The fact they could match older 737s flight characteristics for a more speedy approval from the FAA was just gravy.
> Pitch changes with increasing angle of attack, however, are quite another thing. An airplane approaching an aerodynamic stall cannot, under any circumstances, have a tendency to go further into the stall. This is called “dynamic instability,” and the only airplanes that exhibit that characteristic—fighter jets—are also fitted with ejection seats.
So arguably the existence of MCAS in the first place indicates that the aircraft design is dynamically unstable (otherwise MCAS wouldn't have been necessary).
MCAS was needed to maintain original 737 type specification which allows 737 pilots to fly any 737... significant operational flexibility & cost savings for airlines.
Commentary from blancolirio who is a current 777 pilot. https://www.youtube.com/watch?v=zGM0V7zEKEQ&t=0s
However, my understanding is that the reason why MCAS was needed to maintain the original 737 specification is because of the "pitch up" behaviour on increased AOA (which is what is being described as "dynamic instability" in TFA).
The video you linked doesn't disagree with this -- though it's phrased as being primarily there to "replicate the same feel as earlier versions of the 737, by giving a little bit of nose-down trim". The article claims that being dynamically unstable means that at high-AOA you get nose-up lift (I'm not a pilot or aeronautics expert, so this might be an incorrect definition -- but I've not seen anyone disputing that definition nor disputing it's against FAA guidelines).
If you need an additional system to "replicate the feel" of not having nose-up lift at high-AOA that tells me that your plane design must therefore have nose-up lift at high-AOA. The guy in the video then goes on to say that it's an inherently stable design, but he doesn't really qualify it (other than saying that all other 737s are stable designs) and goes on to say that "the nose goes a little bit light".
Obviously we should hold back judgement until we know all the facts, but "the 737 MAX is an inherently stable design" is not someone holding back judgement.
Dynamic stability is a tendency of the plane that flies straight and level to maintain this straight and level flight. MAX 8 still has this property, MCAS or not.