The "years of experience with a language" is a question for non-technical recruiters. They need some sort of proxy for skill, and length of time is the best one

The "years of experience with a language" is a question for non-technical recruiters. They need some sort of proxy for skill, and length of time is the best one they have. I don't think any actual technical engineers would use this metric when deciding who to hire. It is solely to appease the resume gatekeepers.