U2F administratively disabled based on User Agent despite functioning plugin

Even though Firefox does not support U2F by default, there's a working U2F plugin that works well (tested with Github and Google), but Bitbucket won't even allow the use of U2F if it does not see Google Chrome, and prints this message instead:

"Your browser doesn’t support the FIDO U2F standard yet. Get the latest version of Google Chrome if you want to use a security key device"

It's a shame this is based merely on User Agent and not the actual capability of browser, which can obviously be extended with a plugin.

Attached are two screenshots: one from Chromium demonstrating correct behavior; and one from Firefox showing the error.