I don't agree. The body needs to be conditioned to cope, that's all. It doesn't carry anything unless you have a pack on your back.
In fact it's quite the reverse. You and the mind direct the body. Without you and the mind conditioned you cannot do Aikido.
It's like saying a car improves you. The car does nothing without you driving it. The car is maintained. The rest is nothing to do with the car. Purely down to you knowing how to drive.
If the spark plugs are fouled, tires are flat, one or two missing, out of gas, missing the starter motor...or like that....no matter how conditioned the driver is they go no where.....and even a condition mind can carry the car...... just like cars are not maintained so bodies are not. sitting zazen in seiza for twenty years may settle your mind, but mostly it gives us tight a#$ white guys bad knees, it does nothing to help lineup the transmission of whatever you are transmitting out of the body to effect whatever it is you are trying to effect......... All three need complementary work to be efficient. What I have seen most of my life is heavy work on spirit and mind....thinking that practice of waza 3 times a week as a single approach to body work is enough..... maybe with a cooperative approach to practice that is enough, but to be effective past a preliminary level it is not.. ..... find a middle ground here or you lose me completely....