Open: Greetings dialog appears by default. Whenever a user closes the greetings dialog on any page in the website, the greetings dialog automatically gets hidden on all the pages of the website. Greetings re-appear only after the user clicks on WhatsApp.
Here, User Action is the key. If a user closes the greeting dialog, then it is closed on all the pages. If a user opens on any page, it will open by default on all the pages that the user visits.
Close: The greetings dialog is hidden by default. Greetings appear only when a user clicks on the WhatsApp button.