Perhaps they're building "next gen" machines and using them to replace S5s in their cloud operations, then turning around and selling the used S5s as "new"?
Hmmmmm - where have we heard THAT sort of thing *cough KNC cough* before?
They never claimed the hashnest S5's are new, so that can very well be the case. They have probably been selling used units in hashnest for a while, but as long as there are no issues of them breaking, etc.. I guess it doesn't really hurt anyone.