No. This design is not OK for security.
OK, I stand corrected.
And gratefully so.
It’s moot now anyway for me at least, as I told amarok I completely disabled any sort of address bar “features.” AND added a search bar pointed to my own choice of search engine (which I forget to use). All via settings available in the Arkenfox config files.
I can probably be fingerprinted on account of some of my customizations, but my main motivation in adapting arkenfox’s stuff was to get the browser to behave as I wanted; any fingerprinting relief it gives is a bonus. And in any case, as a QubesOS user, I run firefox on disposables anyway so every time I open it, it’s a fresh custom install.