> Having someone speak your native language makes things infinitely easier to understand and more engaging.

I don't really disagree with this. However, it's only axiomatically true if you hold teaching skill constant. I once learned far more on Tuesdays and Thursdays from a brilliant teacher who spoke no English than I did on Mondays and Wednesdays from a perfectly bi-lingual instructor who was only meh.

When I taught ESL I held onto English-only except in extremis. Knowing (though only a bit of, in my case) the other language, could otherwise become unproductive. As the teacher, it was on me to find the four or five (or however many were necessary!) ways to get to the concept in English. Hearing all of them may have only been necessary for a few of the students, but hearing them was re-inforcing for the students who had 'got it' first time.