When the news about this resurrected editorial board of advisors was given, some sentences were about the systemic bias in the EB content.

‘’There has to be far more attention to the Third World, to women, to alternative political groups, to alternative literature, and things and ideas that weren’t covered by the old Britannica, which was a white male thing.”

So one could simply assume that if the problems were mentioned in the press by Dillinger, EB would also mention the attempt to counter them somewhere.

You are right: The actual work can be done privatly. That does not mean that any trace of work has to be kept that way. In fact, I would applaud to that under the aspect of transparency. PR still could stress out any new lemma that wasn’t covered before or any shift in the focus of the topics or similar. That wouldn’t be an XOR decision.

I’m not aware of any specific public reports from or about the editorial board of adviors. It’s not clear to me why you would necessarily expect there to be some. Their role really is to advise EB on editorial direction, not public relations. It’s not suprising that this work would be done in private.