to short a penny stock you are required to have $2.50 margin per every 1 share short.
so if 1,600,000 shares were sold short it would require a trader to have $4,000,000 to secure that short position.
my point is, people are not shorting a sub-penny stock; i think that otcshortreport.com system is mistakenly tracking sell volume as 'short-sale' volume.