It's not nonsensical at all. Both are platforms capable of storing data and running software using this data. AWS, Azure as well as Postgres offer auth, queue

It's not nonsensical at all. Both are platforms capable of storing data and running software using this data. AWS, Azure as well as Postgres offer auth, queues, triggers, functions, document and table storage, and so on. Yes, you can run Postgres on Azure; and you can run Azure on Azure, or Azure on your own bare metal, or Azure on VMs. I'm pretty sure it'd be possible to get Azure running on Postgres.