Just tinkering with a perspective that bounced around my head just now.
There are two frames of mind when doing paired martial arts training.
Permission is "softer", and honesty is "harder". Both of these things are important, and both pose problems.
Permission is when partners agree to be softer or slower. It is often timed and paced.
This is very important because people are fragile and make mistakes. Simple things can cause serious injury.
This is also very important because people are uncertain and even frightened. Softness helps coax beginners out of hesitation.
This is part of where kata and other solo-work are from. Choreographed movements are on the one hand embarrassing but on the other are necessary. Attaining comfort with ones own movement isn't a trivial thing, and working with a partner is much easier when ones own movements can be reasonably controlled. It's also best to not "waste someone else's time" by training such basic things as how to move or simply stand.
Permission-work can be thought of as a good beginning-point, but the more skilled partners become, the more value they can have from this.
"Honest" work can be thought of as harder and faster. It is more "real".
Most would think this is about reflexes and fast-force, but it is, at its core, about psychology. By pushing the boundaries of permission, it helps draw out inner character. At its beginnings, honest work helps thaw a person from fear and have them act, if only in self-defense.
Where choreography could be considered one of the pillars under permission-work, exhaustive exercise seems to be under honest-work. A fitter body is is just as sought after as a harder mind.
The break between permission and honesty ∞
There tends to be a tension between these two mindsets, often leading to philosophical chasms and the separation of entire martial arts and schools. Concepts of hardness and motion have been created to explain things, but I find these concepts are more easily understood at the very personal and psychological level.
Soft, permission-based work is a good starting point, so as to judge interest and begin the basics of physicality. Lazy and stupid people make for worthless training partners who at best waste time and at worst are dangerous to train with. However valuable this sort of work is and however amazing someone is at their choreography, it's never going to be real until tested. Sometimes skill with a dance is enough, even in physical conflict, but many worry it is not enough and its limitations may lead to real danger.
Hard work is arrogant without being tempered with softness. Adrenaline and perception of skill cloud judgment.
Without a start in permission-work, honest work will lead to injury. "Tough" people will muscle through such problems, but it is ultimately inefficient training. Slowing down and taking the time to understand the different body types and psychologies of training partners will help universalize ones skills. Thereafter, speeding up and working against hesitation will help "functionalize" ones skills.
There is never a complete separation between these two "sides". Something as hard as boxing has shadow boxing and a hell of a lot of tactics and psychology. A martial art which plays at being adamantly on one side of this coin will always have a streak of the other running through it.