By the way, Google Cloud recently launched in-place upgrade of Postgres instances. A few days ago we used it to upgrade our multi TB database in my company as well.
https://cloud.google.com/blog/products/databases/cloud-sql-l...
https://cloud.google.com/blog/products/databases/cloud-sql-l...
The biggest problem with all the cloud providers is that you won't know exactly when this 10 minute downtime window will start
I guess the only advantage here is that you don't have to do 9->10->11->12->13->14 like in the past and maybe that was one of the blockers Azure has. AWS allows to skip some major versions but 9->14 is not possible.
The benefit of an inplace upgrade for postgres is you don't have to spin up another server, restore from backup, and run pg_upgrade yourself.
On top of that Azure postgres (limited to pg11) has essentially deprecated in place of their v2 Flexible tier with no official migration path.