SharePoint Online Tenant Client issue RemoveSite and Restore

Please follow below scenario using your browser: ( I tried in IE and Firefox)

1. Go to http://-admin.SharePoint.com
2. Login as administrator
3. Try to delete a site collection Note: You can delete a site even when you are not the admin (you don’t have access to the site)
4. Try to Restore the site Note: You are able to restore the site even when you are not admin (you don’t have access to the site)
5. Try to run an existing workflow after restoring the site -> you can run the workflow without any issue.

Now if we do the same scenario using Microsoft.Online.SharePoint.Client.Tenant.dll behaviour is different:

1. You are not allowed to delete a site that you are not the admin.
2. However, you are still able to restore the site.
3. You are able to run existing workflows, and you will get an error: “Something went wrong. To try again, reload the page and then start the workflow”

in other word, using tenant.dll only an administrator, who is not the admin of the site collection is not able to delete the site collection, which is quite useless ...

I am not sure if this is a SharePoint Online issue , or there is any trick or workaround to delete site collection using same method.

Note: I don't want to use SharePoint Apps

I have implemented my code based on MSDN official documentation 

[UPDATE]

I have found a workaround by using tenant.SetSiteAdmin() but still behavior is not desirable. as if restore the site collection, there will be additional administrator in site collection administrators.