Don't you think that Amazon possesses a huge bag of Bitcoin already? Jeff Bezos could have easily said to his accountants even years ago to put a billion USD into Bitcoin. It wouldn't even have hurt them at all. I can't imagine that they literally own zero Bitcoin at this point. They could have bought 100,000 BTC like three years ago with what is pocket change for them.
If Amazon already had bitcoin, we'd already know by now. Since Amazon is a public company(and a company with A LOT of investors), they're required to be fully transparent on what they're doing with the company's finances.