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