Article does not compare like with like. It is comparing Donuts and Apples.
Operating cash balance v Cash and Marketable Securities.
That said, it is blindingly obvious that if most of the world's governments are in debt up to their eyeballs that other investors (such as Apple) have purchased the government issued marketable securities. There is no shortage of wealth around the globe equal and opposite to the debts.
Basic double entry bookkeeping tells us that every dollar of creditor liability is someone else's dollar of debtor asset.