In my opinion, if you're hiring for an expert in a specific language, you're not hiring a software engineer, you're hiring X language developer or X language software engineer. The language needs to be explicit in the position listing and perhaps even job title. That's fine if that's what you want but be specific about it so you don't waste people's time looking for a language specialist when most people anymore are generalists that have all sorts of knowledge distributions for any given set of technologies but can most likely adapt and learn to fit your distribution of technology given just a bit of time and opportunity.

Modern development requires juggling too many technologies for most people to specialize in a single language unless their career goal is to niche themselves to that language.