I grew up in California and had the opposite experience. I had friends who grew up speaking Mexican-Spanish at home, and would take the Spanish classes to get an easy A.

The teachers never understood what the Mexican-Spanish students were saying, and kept telling the native speakers that they were doing it wrong.

Does Firefox do reproducible builds? This bug report makes me think it doesn’t (at least for Linux): https://bugzilla.mozilla.org/show_bug.cgi?id=885777

But maybe they do for Windows/Apple/Android?

If you liked vimperator, you might like https://qutebrowser.org/