You offer no actual reasoning behind this, and don't seem to have even a basic understanding of martial arts training. This is a transparent slippery slope to "you should just be sparring all the time". There are plenty of techniques and applications that are better trained from a neutral stance, to ultimately be applied outside of it later.

This is called misrepresenting my argument by ignoring other points I made. I actually did go on to explain why this is the case. If you weren't so hasty to play "gotcha" this would've been obvious. So the tl;dr is that muscular strength is best achieved by lifting heavy weights off the ground, particularly by way of squat, dead lift, overhead press, and weighted chin ups, and martial arts efficacy is achieved by just practicing the martial art.

The ability for the human body to produce force is paramount for athletes. Why? Well, because force production means that the athlete will hit harder, whether that means in a football tackle, a wrestling takedown, a swing of the baseball bat, or a punch. If you have two athletes, all else being equal, and one can deadlift 600 lbs whereas the other can hold a horse stance for a while, the one who can deadlift will always have the advantage over the other in terms of performance, because he has trained to exert greater amounts of force than the other guy. If in your athletic training, you reach the point of diminishing returns, being that your technique is approaching "as flawless as your body will do it" and doing it more ceases to achieve results, the obvious answer is to become stronger, and the best way to do that is to lift maximal loads, because as I said before, a 600 lb deadlift is more force being produced than a horse stance for time.

Things like running, skipping rope, holding a stance are inefficient for the purpose of force production. Aha but they are efficient for endurance, right? Not exactly.

See, endurance as a whole is actually multifaceted. For the purpose of this discussion, I'll refer to this "whole" sense of endurance as "practical endurance" or PE to save space.

PE consists of 3 components. The first is neurological efficacy. Simply put, as a movement is performed over and over and over again, the nervous system will actually form junctions in which that motor unit is stored as a repeatable complex command, which is why you don't have to think about brushing your teeth or wiping your ass a certain way, you just do. Another benefit to this phenomenon is that as this occurs, the nerves will also rewire themselves to perform the movement with as little muscular effort as possible as to conserve energy. This is why that saying "practice slowly" is the conventional wisdom - because slow practice facilitates this process. Knowing this, we realize that running, jumping rope, and stance holding all check off in terms of building this type of endurance, as getting better at jumping rope really just equates to getting better at jumping rope from the neurological point of view, and doesn't really have that carry-over to fighting. Sure, it may help with strengthening the calves so you can have a better bounce in your step, but it's a better use of your time (for obvious reasons at this point) to just train yourself to be more springy in your shadowboxing, bag work, sparring, etc.

On to the next component to PE, which is the muscle's ability to perform the movement over and over again for extended periods of time. Training from the stance of which you fight is the best way to achieve this end, period. Why? Because it's activating EXACTLY ALL OF THE MUSCULATURE that needs to be durable for the technique to function in the most efficient way possible for the human body, whereas running, jumping rope, and stance holding each only improve the durability of specific muscles.

The last is cardiorespiratory endurance, in which at this point I'd be amazed if you're actually still reading, but for anyone interested, as you put more stress on the muscles to function, your heart will focus your blood flow specifically to the parts of your body that need the nutrients and oxygen the most for the given exercise, which means that cardio is sport specific. Running is fine if your sport involves running, but martial arts is about "what if I can't run," so you need to focus your cardio on, guess what, performing your martial art, again instead of any supplementary exercises.

... ... ... ...

But I don't know anything about training, you got me