Aren't most interviews like this? Most dev openings I see posted mention the specific language who's expertise they're looking for and the number of years of experience needed working with said language as well.
It can be annoying, but manageable. I've never coded in Java for example, but knowing C#, C++ and Python I imagine it wouldn't be too hard to pick up.
Huh, okay. That's not how we run interviews but I guess it's at least a thing, even if not common around here that I've seen yet (I'm not super current on interview practices though)
Regarding the job ads, yes they'd describe the ideal candidate but I haven't the experience that the perfect candidate ever actually shows up. Like you say, knowing J, T and Z, the company is confident enough that you'll be able to quickly pick up dotting the Is and crossing the 7s