I don’t think anyone can claim to understand it completely. There are some parts of the text Chinese text that are very difficult to interpret in any useful way.
However, I think I understand his strategic approach pretty thoroughly, or well enough to have written about forty books on the topic. My books have won a lot of book awards, sold a few hundred thousand copies, and been translated into a dozen or so languages, so people seem to think that I understand enough of it so that they find it valuable. I also used these idea to build an INC. 500 company, so I understand something about competition in the real world that I got from Sun Tzu.
I think that anyone who reads one of my books on the topic can understand the basic of the book and feel confident in reading any decent translation. They should understand these ideas well enough to use at least some of them in their own competitive struggles.
Sun Tzu’s book is written more like mathematics equations than English sentences so a lot of it is pretty formulaic. He lay out his basic axioms first, then his theorems. This means that, given the right approach, an accurate interpretation has a high degree of consistency. And a poor interpretation runs into problems everywhere. However, there are different levels of understanding of formula. People can understand E-mc2 well enough to discuss the idea without understanding it well enough to do the physicas.
This is the reason I showed all the original Chinese characters individually translated in my Chinese Revealed version. It allows those who can’t don’t understand the ancient Chinese writing system to compare these formulas to the “translations” that others provide of the work. What is revealed is that most English “translation” mix the translators opinions about Sun Tzu’s ideas with his words in such a way that it is impossible to get at the real heart of his work.
Of course, as with every area, experts disagree. However, the only experts whose opinion I value are all in China. I may bot always agree with their views, but I respect their expertise. They know the text. And most aren’t as sloppy in their work as I am.