I understood “this” to mean “borrowing [more stock that actually existed] and shorting”.

As your link explains “Naked short selling, or naked shorting, is the practice of short-selling a tradable asset of any kind without first borrowing [...]”

After someone has setup a covered short, the stock they borrowed and sold is again on the open market, is it not? And thus could be lent out by the new owner, enabling a second covered short?