I'm fine with calling Blink based browsers "Chrome skins" and WebKit based browsers "Safari skins" but only if we all understand that "skin" isn't just a cosmetic thing. Firefox on iOS has its own features, settings, history, bookmarks, sync system, and other stuff that can create real, noticeable differences. Even if you assume "skin" means just the UI behavior, wouldn't it make sense that there could be a Firefox-specific bug with the URL bar?
This sounds exactly like my issue (and I have even experienced it with the exact site in the bug report, reddit). For some reason I did not even think that the firefox iOS app would have an open source bug tracker but of course it would. Also had no idea it was called the 'awesome bar'.
This is just a sign I should spend more time on HN and less on Reddit.
To answer the GP's question, this does sound like a known Awesomebar issue that might be improved with a future update to the Places database: https://github.com/mozilla-mobile/firefox-ios/issues/11775