We did confirm with our Product team that we don't have a way to expose this information at this time. We can definitely take a feature request for this. They also want to check why you need this information and how it will help you.
With Managed service, the expectation is the cloud service to automate and provide you with the ability to do point in time restore and you can validate it and hold Microsoft accountable for this.
Also for raising the Feature request on MariaDB User Voice.
Thanks
Navtej S