In the end it doesn't matter, as long as we can perform point-in-time restores and as long as the IO isn't paused during a backup, which happens with DPM when it backs-up files unrelated to SQL Server.  It's more of a curiosity to better understand what is being used by Microsoft.  If Microsoft is using DPM in Azure PAAS, then perhaps that is something we should also consider for IAAS.  It was a question I wish I asked at Ignite.  Adding to the curiosity is the introduction of another form of PAAS, Managed Instance, which re-introduces the SQL Agent.

Thanks,  Dave