Set PDF file so that is opens without showing the bookmarks panel.

I'm using Acrobat Pro 2024.005.20399.

Despite having set Document Properties > Initial View > Navigation Tab to "Page Only", my PDFs are still showing the bookmarks panel when they open.  I want them to open with the Bookmarks Panel hidden. 

Theses PDFs consist of a single page and have no bookmarks in them.

To make them come up without the Bookmarks Panel showing, I've had to add an Action to the page:

Select Trigger = "Page Open"

Select Action = "Execute a menu item"

And the menu item I've selected is "Acrobat Menu>View>Show/Hide>Side panels>Bookmarks

When I do these things, the pdfs finally come up without the Bookmarks Panel showing.

So, I can get it to work, but I thought that merely setting the Navigation Tab to "Page Only" would be sufficient to work on its own.

What's going on?  Am I misunderstanding something?

I'm attaching screen shots of my document and page settings.