Let's consider Napoleon - the Yogi Berra of military analysts - as a counter example:
I have fought 60 battles; and learned nothing that I didn't already know in the first.
Yes; we know. And it really shows. No wonder you followed that statement up with:
Do not fight too often against the same enemy; or you will show him all your art of war.
Not one of those he vanquished was so vain, and incapable of reflection, to disdain learning from either success or failure.
Boney did have 3 particular skills that served him well:
Mastery of Grand Tactics (now termed Operational Art) comparable with the very best military commanders of all time; and at least arguably he might have been the best ever at this.
He revolutionized the use of artillery in his age; but as others witnessed this, the principles that Napoleon introduced were soon copied even if not always perfectly.
The capability to inspire fanatical loyalty from not only the French soldiery, but subordinates who wouldn't give each other the time of day; and even, such as with Bernadotte's actions during Jena-Auerstadt, worked to arrange the defeat of colleagues.
When Wellington observes that Napoleon's presence on the battlefield is worth 40,000 men to the French, it is this trait in particular that he references.
However, as a battlefield tactician, Napoleon is far from even being the best French commander of the Napoleonic age. At a minimum Davout and Suchet surpass him at this; and others such as Massena, Desaix, and Lannes certainly rival him.
These are not the characteristics of a great and insightful author. Yes, some of Napoleon's comments on war are insightful; others can be twisted into possession of depth possibly unintended by the author; and others such as the two quotes above are merely risable as anything except a warning against hubris.
Finally: observe that the act of writing a book, and particularly a tome, is one of the most introverted of acts. In contrast, the exercise of command is one of the most extroverted. Finding both these extremes in a single individual is rare at best.