Officially, hoarding has never been allowed. You can't buy IPs unless you have a plan to use them. And there's nothing strange about a company with tens of millions of VMs buying tens of millions of addresses.
People hoarded toilet paper when Corona began with full intention to use them. People hoard food in wartime with intention to eat it.
So yes, Amazon hoard IPv4 with intention to maybe use them in the future. But hording it is, and in a non-hoard system they'd rent - not buy - IPv4 with a month notice or so.