If you see a message “A critical software update is required for your Mac. Connect to a network to install this update” that looks like this:
This is NOT Bartender and isn’t anything to do with Bartender, it’s the macOS Setup Assistant and its icon, see both images below:
This is macOS Setup Assistant:
This is Bartenders Icon:
As you can see very similar, but different, Apple just chose a butler icon for their setup assistant icon.