Anyhow, I think what you mean by shorting in this sense is that prices are going down due to shorters, while the people taking the long positions are doing so when the markets are falling. If that makes sense.
You seem to not fully grasp what OP wants to say. He basically says that if the number of those who open short positions increases, so must the number of those who are taking long positions as there are always two sides to the trade - the buying side and the selling side. When one trader sells to another, it is always the case. But things become more complicated with margin trading when a trader doesn't sell his own coins as he first borrows them and sells them on margin.
So if people expect prices to fall, they may borrow more money to ride the wave down. In this case, the amount of borrowed money is expected to match or matches the number of open short positions. But as I said in my previous post here, this is hardly a bullish indicator.