Among the most favourable readings in this hexagram, nine in the second place withholds nothing. Good fortune is stated, advancing is called advantageous in every way, and no condition is attached to either. A querent drawing this line on a question about approaching an opportunity, an office or a person of influence is being told that the movement is sound and that the usual cautions do not apply at this stage.
The commentary's note that the subject does not yet entirely follow the commands from above is the practical heart of it. Readings landing here often involve someone advancing under an authority whose instructions they do not follow to the letter, and the text treats that independence as part of why the advance works. A strong line in the second place, central though incorrect for an even position, is expected to bring judgment of its own rather than compliance.
The caution is only about company. This line advances together with the strong first line, not against it, and the good fortune belongs to a movement that keeps the partnership intact. Independence from the authority above is endorsed here; independence from the ally below is not what the line describes, and a querent who reads it as licence to act entirely alone has taken the wrong half of it.