The requirements were probably written by someone else and then copy-pasted. The poor recruiter likely doesn't even know what Kubernetes is. You simply explain

The requirements were probably written by someone else and then copy-pasted. The poor recruiter likely doesn't even know what Kubernetes is. You simply explain to them Kubernetes itself didn't exist at the time, but you have experience with related technologies (Docker, Linux, whatever, etc.) If you communicate well, they'll present you to their client regardless. Remember, they want that fee.