I think the 4 TiB limit is for ASR. Backup is larger now. Here is the paragraph you may want to correct:
Azure Backup support
To protect against regional disasters, Azure Backup can be used to create a backup job with time-based backups and backup retention policies. This allows you to perform easy VM restorations at will. Currently Azure Backup supports disk sizes up to four tebibyte (TiB) disks. Azure Backup supports backup and restore of managed disks. Learn more about Azure VM backup support.
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@stdistef
Thanks for the feedback! I have assigned the issue to content author to check and update the document as appropriate.
@roygara
Can you please check and add your comments on this doc update request as applicable.
@stdistef Thanks for reaching out! I've gone ahead and confirmed that it is up to 32TiB at this point. I'll update the doc accordingly, it'll be live later today.
We appreciate you helping improve our docs, thank you! :D