This feature lets you assign a customer to a gallery as the owner of the gallery. When you do that, they have the option to hide photos in their gallery so anyone they invite to view their photos can not see those hidden photos.
Plus: if someone tries to view the gallery and don't have the password for it and uses the request access to the gallery feature, that email will be sent to the gallery owner instead of you.
Plus: (Starting with Sytist 1.4) If you have a gallery with password protected sub galleries, a gallery owner will be able to view all the password protected sub galleries without needed the password.
Notifying Gallery Owner
After you have selected a gallery owner for a gallery and saved, there is a link to email them about their gallery. In the email it explains how to hide photos.
It is important that they log into their account in order to use that feature.