Niko Neugebauer moves the backups pretty far away:
The new Geo-Zone Redundant Storage (GZRS) backup storage option combines the best of two worlds – Geo-Redundant and Zone-Redundant storage, keeping backups safe from both regional (Geo-Redundant) and Data Center (Zone-Redundant) failures. It provides the highest availability for storage currently offered on Azure, improving recovery speed and enabling Point-In-Time Restore (PITR) of backups in the event of a zone failure.
Geo-Zone Redundant Storage for Azure SQL Managed Instance backups provides 3 synchronous copies in different availability zones within the same primary region, plus an additional asynchronous copy within a single availability zone in the paired secondary region, as shown on the following picture:
Click through for that picture and what it does for expected availability. Basically, a whole bunch of data centers would need to fail before you lose a backup. Or someone messes up DNS and makes everything unavailable for a day, not that that’s ever happened before with a large cloud service provider…