Global Admin Showing up with Access to All Users OneDrive for Business

Sure, I got it directly from Microsoft - here is the script:

Powershell command to attach to someone's OneDrive as a secondary Administrator to copy files:

 Open SharePoint Online Management Shell - run as Administrator

Copy and run this script below replacing the user's name and using underscore between user first name and last name and yourcompany.com

Set-SPOUser -Site https://amtrak-my.sharepoint.com/personal/FirstName_LastName_amtrak_com -LoginName Your.Name@yourcompany.com -IsSiteCollectionAdmin $false

Then hit ENTER to run.

NOTES:

$true adds you as an Admin to their OneDrive

$false removes you as Admin to their OneDrive