Linked apps mystery

OK again -- I now realize this is the scenario that resulted in my confusion:

1. Open a new browser window or Finder
2. Instead of pressing Shift-Command-Space to bring up Quick Access, inadvertently use muscle memory from 1Password 7 and press Command-\
3. In the Quick Access window that appears, begin typing the name of a website and click Autofill or press Return, which brings up an alert popup ("Would you like to link your 'Mac Login' item in 1Password with your macOS user account login?")
4. Click "Fill Once," which does nothing
5. Click "Fill & Update Login," which adds the browser or Finder to a Linked Apps section in the Login item but does nothing else

So, the lesson is, don't use Command-\ to bring up Quick Access in a blank browser window or Finder.