I use Mac most of the time and I’ve found that the functionality on Mac has largely started following how 1Password works on Linux. Meaning that the desktop app functions as a standalone app to modify your password records and the browser plugin allows you to access or lightly edit those records. Older versions would let you call the desktop app with a simple plugin but since I switched to the 1password.com version that’s no longer the case. If you’re on 1Password 7 then what you’re saying makes sense.
As an aside, the function I use by far the most on Mac is command-shift-space to pop up a password search dialog that works very well. Not sure if that function exists on Linux.
I stand quite corrected. I learned a lot about native messaging on Ubuntu and understand where you’re coming from!