Storage of other speakers in the room, shorting them while not in use? Myth or true?

Never heard of the "shorting" solution....but Ivor - the founder of Linn --  would not allow any other speakers in a room that his speakers were being demo'd in.  He claimed that you couldn't get an accurate representation of his speakers with others resonating in the same room.

I'm sure they no longer have that requirement -- but that was the case in the "old days". 

Better to remove the speakers altogether - you get two effects from the presence of another speaker. One is the drivers will act as passive radiators to one degree or another - depends on the size and proximity as well as the volume of the driver cavity. The other effect is from the enclosure - think of a Helmholtz resonator. This can especially affect the bass depending on your speaker design (ported, folded line, etc.). 

There are of course lots of variables to the degree and type of effects - speaker design, proximity, and room placement to name the main ones.

I got a real chuckle out of the aforementioned article by Bill Sommerwerck in the Stereophile magazine in which he mentions a reviewer's  "One Speaker Room" devoid of any other speaker including a telephone.  When he pointed out that the reviewer had a low coffee table directly in front of the listening position which would act as a reflective surface, it reminded me of another typical listening error.  Listening while wearing eyeglasses is the same as placing a reflective surface just inches from your ears.  I noticed it when I switched from eyeglasses to contact lenses.  What a crazy, but interesting, hobby !

You shouldn't be in the same room.

Rather than wondering or trying to sort conflicting opinions why not simply try playing music first with the added speakers in room and the current ones playing. If you notice no difference than the question is answered for you. 

Taking it a step further, switch speakers and listen again. What you can overlook is not there. Actual experience is the most reliable measure.