additional rec for language/exchange?

I’m deeply invested in studying Chinese. I’ve done an immersion camp, lived in China for two months on a school sponsored exchange, am president of NCHS at my school and will have been taking it for all four years of high school. Since Chinese is such a big part of who I am, naturally I would want a recommendation to attest to this, however due to weird circumstances at my school the teacher I had my first two years left, and we still don’t have a permanent replacement. I have no one at my school now who can write me a solid rec, and my director/head at the immersion camp is volunteering to write a recommendation accompanying quotes from my current Chinese teacher and chaperone on the exchange. Does this seem like an appropriate reason to add a supplement or is it a waste? I know Yale’s cited example was summer research and I’m not sure if this is comparable. I’d love for some input!

What is the absolute MOST the director can say besides @gongongqiche is fluent in Chinese because they have been so dedicated to learning the language. Would an Admissions Director at Yale be able know that from the rest of your application? I suspect they would, especially if you write a supplementary essay about your love of the language. So, I think the additional rec would be superfluous…