Get-PowerBIActivityEvents returns a list of objects with empty list attributes

I have the following code: 

$start = (Get-Date).AddHours(-10).ToString("yyyy-MM-ddTHH:mm:ss")
    $end = (Get-Date).ToString("yyyy-MM-ddTHH:mm:ss")

    # Don't pipe through Out-String or ConvertFrom-Json
    $activities = Get-PowerBIActivityEvent `
        -StartDateTime $start `
        -EndDateTime $end `
        -ActivityType 'ViewReport' `
        -ErrorAction Stop | ConvertFrom-Json

    $activities[0]

That outputs the following:

Id                       : {}
RecordType               : {}
CreationTime             : {}
Operation                : {}
OrganizationId           : {}
UserType                 : {}
UserKey                  : {}
Workload                 : {}
UserId                   : {}
ClientIP                 : {}
UserAgent                : {}
Activity                 : {}
ItemName                 : {}
WorkSpaceName            : {}
DatasetName              : {}
ReportName               : {}
CapacityId               : {}
CapacityName             : {}
WorkspaceId              : {}
ObjectId                 : {}
DatasetId                : {}
ReportId                 : {}
ArtifactId               : {}
ArtifactName             : {}
IsSuccess                : {}
ReportType               : {}
RequestId                : {}
ActivityId               : {}
DistributionMethod       : {}
ConsumptionMethod        : {}
ArtifactKind             : {}
RefreshEnforcementPolicy : {}
BillingType              : {}

I am trying to figure out why I am getting objects for which each attribute is just an empty list. I have followed the official documentation for this Cmdlet but I can't figure out why this is happening. 
I've also tried not using ConvertFrom-Json and just log the Json string. However, I get the same result. 

Documentation I'm following: Access the Power BI activity log - Power BI | Microsoft Learn