Sure but you can't exchange Azure credits for goods and services... other than Azure services. So they simultaneously control what OpenAI can use that money for as well as who they can spend it with. And it doesn't cost Microsoft $13bn to issue $13bn in Azure credits.
>>dixie_+k2
Bitcoin you would be lucky to mine $1M worth with $1B in credits
Crypto in general you could maybe get $200M worth from $1B in credits. You would likely tank the markets for mineable currencies with just $1B though let alone $13B