Hi there,
Thank you for reaching out to us.
You may want to check with the account manager assigned to you by Google in order to check if you are whitelisted to use that feature. If you do not have an account manager, then I would suggest reaching out to the AdMob Help Center for further assistance on this, as I'm afraid that we can only assist you on your technical concerns with the AdMob SDK in this forum. The product specialists there should be able to provide better insights on this.
Regards,
Ziv Yves Sanchez
Mobile Ads SDK Team