Well, I agree that it exaggerates the importance of the (No) Vacancy sign, but it is different in precisely the sense the author is talking about - you have an

Well, I agree that it exaggerates the importance of the (No) Vacancy sign, but it is different in precisely the sense the author is talking about - you have an on/off switch for NO, and another for VACANCY. While presumably no one wants or needs to turn on OPEN and CLOSED simultaneously.