Jkl's body mechanics seem over-exaggerated

I imagine it would be a lot like trying to sword fight with a chain saw locked at full throttle. Try swinging one around sometime, they do not behave intuitively

The sword is described as highly concentrated energy that is rapidly circulating, moving to the end of the beam and back, both of which seem in line with what we see in the films so I am fine with this description. The cycling motion creates angular momentum in the beam, giving the sword a significant amount of gyroscopic inertia. The inertia gives a feeling of "weight" to the sword; it resists motion when you try to swing it.

Milky Way physics says swinging the sword creates a torque perpendicular to the momentum vector because: T=IW' + WxH (torque equal to product of (I) inertia and (W') angular acceleration added to cross product of (W) angular velocity and (H) angular momentum). Of course, this assumes Milky Ways physics and we know Star Wars physics does not always hold to our notion of reality.

But in the Milky Way, when the wielder of such a sword swings it in an arc where the angular velocity vector is perpendicular to the angular momentum vector, an out-of-plane torque is created 90° perpendicular to the plane of intended motion. Say an aggressor were trying to swipe off Jango's head with a nice level cut; the gyroscopic torque may act to swing the blade up and over the top of the target, resulting in a clean miss. The wielder must apply a counter-torque to stay on target. Alternatively, if the angular velocity of the arc is parallel to the angular momentum vector, then NO out-of-plane torque is generated; the sword goes exactly where intended, no counter-torque needed. Then in between the two extremes, varying amounts of counter-torque are needed depending on the sword arc.

Moreover, the wielder must remain aware at times of their grip on the sword hilt because rotating the grip around the hilt changes the position of the (H) angular momentum vector relative to the hand. Say for instance that a "standard" grip orients H pointing UP when swinging a level, horizontal arc. Spin the grip 90° around the hilt, and now H points RIGHT when swinging level, completely altering the counter-torques that must be applied.

All this business about counter-torques is why a Jedi master is much better at lightsaber combat than a novice: they draw on the Force to predict and nullify these effects.

Regardless of the sword arc or grip position, there is always some resistance to the swing because of that first IW' term, which essentially says that the faster you swing it, the harder it is to swing. This is that part that governs how hard it is to swing a baseball bat or a stick, with which most Earthlings are probably familiar.

All of this raises some interesting thoughts, like could such a fantastical sword be designed to have neutral angular momentum to eliminate the need for counter-torques. I say "why not?" This is SW physics, maybe such a device is hidden in the hilt. NASA builds tools like this for astronauts in the MW galaxy, surely they could do it in the SW galaxy. But supposing they did not have momentum neutralizing devices in the hilt ... what would the momentum vector look like for double-bladed lightsabers? Well if it were well designed with equal-but-opposite vectors for each blade, then a double-bladed model would certainly be momentum neutral which would probably make it much easier to control. So while Darth Maul looks formidable swinging around his double-ended death dealer, perhaps what it really means is that he is weak with the Force ... or perhaps he must be dealt with using extreme caution because he is not encumbered with using the Force to control his weapon, leaving him free to use his energies on other Force-draining tasks.

But no matter what they do to try to control the angular momentum problem, there is always the baseball bat component of the inertia which makes it hard to swing.

qed