Get-AZRoleAssignment not showing Groups?

Hello

I'm trying to get an export of all of my management groups, and then check the role assignments for each one.

However, when I run this:

Get-AzRoleAssignment -ResourceGroupName $mgmtGroup.Name

It returns all objects (service principals, users), but does not groups for some reason.

See below.
This is the PS output for Owners using this command:

Get-AzRoleAssignment -ResourceGroupName $mgmtGroup.Name -IncludeClassicAdministrators |Select RoleDefinitionName,ObjectType,DisplayName,SignInName

But there is clearly a group there:

This is really driving me nuts.
Anyone see anything like this before?