This has do to with making sure that each component of our Strength & Conditioning program is done well. By doing each component well we will get the best results. I think this is obvious, once I write it down, but if you want me to explain further just mention it in the comments.
This idea is present throughout my approach to training, not just the S&C part. I'm going to use a few examples below and draw the examples towards HEMA training to illustrate the general idea.
Basically, I don't like exercises that mix different components, like power and stability. At least not as the primary part of my program. And for a person new to strength training, the primary exercises are their only exercises. (I recently argued with someone about kettlebells for strength training; only to realize that he was an advanced lifter and using them as assistance exercises. He just didn't think of them as assistance exercises.)
A kettlebell snatch mixes several different components, while a dumbbell snatch focuses on power development. The dumbbell snatch is unilateral and asymmetric, so it's a bit of stability and core work, but it's mostly about the power. An exercise that is mostly one component (e.g. power or strength or conditioning) and a bit of another is a good thing. It's a good thing for the secondary exercises in a program. The primary exercises should each focus on one component and maximize that piece.
The kettlebell snatch has an off-center weight thereby increasing the stability demand of the exercise - limiting the weight. Limiting the weight I can move limits my power development - so it's not a good snatch. Limiting power development limits the acceleration training of the exercise; and acceleration is how the snatch is relevant to martial arts and combat sports.
Additionally, the KB snatch is technically demanding, because otherwise you break your arm. This means you have to progress slowly and develop the technical skill for this lift. And that is time taken away from technical training for HEMA. A KB jerk eliminates the risk of breaking your, but still has the above problem of limiting weight, and therefore power development.
Lots of LungesWhew, now I'm done talking about kettlebells. Why not do lots of lunges, like a hundred? It's a good conditioning workout, right? Sure, but it's crappy technical training for lunges. Out of 100 lunges I'll get good, explosive power out of the first 10-15. After that it'll be lower intensity lunges. Lunges that won't hit in fight because they aren't fast enough.
But if I do 100 lunges for conditioning purposes then I'll have crappy lunge form. To get a good conditioning stimulus, I have to do lunges at such a tempo and intensity that making them technically excellent is impossible. This is why conditioning exercises are normally limited to those that can be done at huge volumes and remain sound, like running.
I can't do both. I can't have technically excellent lunges and good conditioning. I can't do explosive power and conditioning. Pick one, work on it. Then the next day, pick the other and work on that.
Cyclical/Flow/Parry-Riposte DrillsThis same reasoning applies to this kind of drilling. These drills have different names, but they usually involve a technically simple pairing of an attack and defense. They are partner drill where the roles constantly reverse. I attack - you defend. You attack - I defend. And the attack and defense don't change.
The advantage of such a drill is primarily that you can get large numbers of repetitions out of it. And this leads some to approach these drills as a way to involve a conditioning component into the drilling part of class.
But I disagree. As we push the drill to a level that it's conditioning then we lose technical form. And that's a problem. The drill then begins to lose it's relevance to martial arts training. Either by being sloppy or by decreasing the intensity below that which is used in fighting just to get more time or reps done.
Some coaches do this because they want to make a class that does everything. A one-stop approach to strength, conditioning and technical training. But this means that there are limits on how well each component can be done.
I prefer to set a high bar. I am up front with students that if they want to reach their personal best then they need to be putting the time in outside of class to do the strength work; to do the conditioning work. Class is for technical development.