"Clè" should never be marked correct when "clé" is the proper answer. It's a completely different word! We need to divorce ourselves from the idea of teaching French from an English perspective. These aren't the same letter with accents being an afterthought -- they're entirely different letters with their own pronunciation.
Another way to think about this? Lingvist is teaching sloppy French. Or, if we want to get product-specific, even Lingvist's new pronunciation feature via voice doesn't agree with this.