Stepped down ''as chair'', not from the board as a whole

This article could easily be read to suggest that Wales had stepped away from the WMF board entirely. That would not be accurate. He merely stepped down from his position as chair of the board.

I agree the article would have been better had it been more explicit on the point. I don't agree the article would be all that easily misread in the way you describe; at most I'd see the reader being uncertain on the point on first reading, thus calling for closer study. The article says the board (including Wales) changed its organization, including choosing a new chair. There's nothing to suggest, when the board switches from one of its members being the chair to another one of its members being the chair, that the one who used to be chair would thereby cease to be a board member. (On a historical note, I'm not honestly surprised to find that a short item on a subject whose background all the contributors were likely well familiar with, written several years before adoption of systematic review, was rather sloppy about explaining parts of that background knowledge.)