While no person is exactly the same, and some are more talented or and experienced in one area over the other, still there are universal methods that are more efficient.
When someone is looking for balance in the so called fighting stance, he is not balancing the most critical need of a fighting method - imminent action vs. stance!
In boxing the weight is needed to be shifted to support the punch which at that moment give your body a different stance. Your weight will not be equally distributed on both feet, and your stance will not equally withstand impact or push and pull from every angle anyway.
In Judo and grappling, when you try a hip throw or a leg throw, again you are not going to have both of your feet on the ground during a throw. Balance in grappling is usually mistaken for method of applying counter leverage in the force of push and pull. In Boxing it is usually pertain to putting yourself in a moment where your feet cannot push back for you to evade a punch, or you cannot duck comfortably a punch because you stretch your balance limits way over your base which is the feet.
So again, while average grappling and boxing instructor may tell you you are out of balance, in Pure Krav Maga we strive to maximize reach and momentum under the constraint of reaction time. The lack of so inferred balance, is balanced with a different overall tactical plan.
Finally, the so called fighting stance is explained as a virtual concept that while it helps set your navigational bearings it is never being used in a fight, because you only pass through it for a split second. The ultimate reality should be that your "fighting stance" in Pure Krav Maga would be a normal stance before, a finishing stance after each strike and kick which enables you to execute the next move if needed, and a final normal stance after you finished your business and feel like standing instead of sitting...
The virtual training stance, however, is almost like a boxing stance where gives you the comfort of advancing and retracting in and out of the hotzone quickly. Through that "stance" you learn the mechanics of efficient motion.
But in reality, unless you are one of a kind, you will always start from the position you were in. If you need to react quickly, you simply skip the training position and move for your strike or kick.
As for those that think they should get close to someone in a ready position to attack in case, they are in fact putting themselves in danger unless they do assume the position and attack at the same time. They simply telegraph their capabilities and also limit them as they step into the hotzone. They would not have the time to react to a preemptive attack and the attacker will be able to see where their arms and legs are prior to their entry of the hotzone.