Thanks for the link. When OUR MCC invites a customer's MCC, the customer is presented with a disclaimer saying:
Grant XXX access to this account?
If you grant XXX access to this account, they can change and manage your
entire account, including all ads and keywords, as well as accept Terms and Conditions
on your behalf. They won't be able to change your Google account's email and password.
If you don't know this manager, and feel this is an unquthorized attempt to access your
account, you may contact us and report a complaint.
Our customers will STOP at that point and say "no thank you." Our UI access appears to be read only but this

text says otherwise. I know this isn't an API issue, but we appreciate you helping us.