Stated intention and actual intention are different.

And besides, even if that is the intention... this company is way too big and influential to be making blatant privacy violations and having internet commenters try to sell the public on a corporation's ethics.

Yeah... the article is pretty garbage. If you have given the Facebook app permission to use your camera, it can use it whether it's showing you a frame in the background or not. The tweet in question is merely showing a bug that happens to speed up the loading of the camera UI. If FB is spying on users, they're doing it whether this article is true or not.

Facebook is not entitled to the benefit of any doubts.