"selling at a loss" generally means that the margin is negative, that is the unit price to manufacture (and ship, etc) is higher than the price the consumer pays.

Your alternative definition applies to pretty much everything with R&D costs. The first unit sold is pretty much guaranteed to not make up for R&D costs, but for some n the margin made on the nth unit covers it, and the seller finally starts turning a profit.

I think what your citations are actually saying is that even the last unit sold does not cover R&D costs, and it has to be made up in other divisions (such as games) in order for the whole venture to turn a profit. But each individual unit is still marginally profitable - if they could sell enough of them (perhaps far more than the size of their market) they would eventually turn a profit on the console itself.