I didn't read this as "pair program every line".

I write a bunch of features. Most are pretty boring. A junior isn't going to learn much by pairing. But occasionally, I do big architecture changes. Those ones are perfect for early collaborative design, pairing, and discussion. The whole team benefits from understanding the architecture better and juniors get to see how seniors think about it. Then you can pair with juniors on the prompting or, more likely, the implementation plan to hand to the agents. That's maybe once a week.