Fwiw, the ferrules on the tube I pictured are not rubber or rubberized. They do appear that way in the picture but they are definitely metal. The tube itself is non-magnetic but the ferrule is magnetic.
Also, I’ve had them on/off many times and have not experienced leaks.
I have edited and renamed the Shoebox Spreadsheet indicating the above conversations. It's renamed as "Shoebox R-1 With Links 11-25-24" and is now attached in this reply. Thanks to all for the valued input! If there is another item, part, piece, widget that needs attention or addition into the sheet, please let me know and I will incorporate, investigate, revise the Box information as needed, applicable.