I don't often interfere with fitting threads but there are various claims made here, mutually contradictory and as well as I can tell as a non-fitter cyclist who has studied physical mechanics, are mechanically wrong.

Can it happen from too short a stem - No. Bending the elbows more with a shorter stem, the torso has the same angle and therefore the same center of gravity, but of course it's easier to hold your weight up with your hands closer than farther away. Keeping the arms the same on the other hand moves the balance back and up, which would reduce the weight on the hands. Physiological effects may increase (or sometimes reduce) pressure on the hands, but those effects are not invariant amongst all individuals.

KOPs has no effect on the weight distribution between the saddle and bars. It changes the direction of force from the legs. It also has another effect, that Clem von Jones alluded to.

The torque lever arm would be operant while riding out of the saddle and leaning forward, but sitting in the saddle the force vector from pedals pushes back from the bars, not towards them.