Doubt - Return of Owner Get-UnifiedGroup

Hello friends,

As usual, I apologize for the words, but I don't speak English and I rely on an online translator.

Well, I have a doubt and I believe it is of orientation.

I have work to do on my structure, which is basically a Tenet with multiple domains "underneath" it, and somewhat loose.

For some time, users were able to create sites on Sharepoint and Teams (which also brought more sites on Sharepoint).

The demand that came to me is to list the sites and analyze how much space each one is using, evidently for billing.

Needless to say, this is getting a little complicated.

I list the sites, the one with @ as owner already identifies the company and the user of this site. When the owner comes only one ID, it makes an analysis via "Get-UnifiedGroup" which in "ManagedByDetails" returns me who would be the owner.

What I "knew" so far:
- By default, the person who creates a group is the owner. All groups must have at least one owner. Group owners do not need to be members of the group.

The Doubt: How is it possible that for example the "Get-UnifiedGroup -Identity [ID of a Group]| Select ExternalDirectoryObjectId, ManagedByDetails" can be empty?

Thank you very much in advance for your help and guidance!!!

Big Hugs!!