I think he's trying to imply that the stereotype exists for a reason, that deep thinking requires isolation from distraction.

For a more concrete example, you can look to what Richard Hamming had to say about the topic. He noticed a similar phenomenon at bell labs, where there was a difference big difference between people who worked with their doors open, and those who worked with them closed.

The door closed people were much more productive than the closed door people. Of course, he noticed there was a tradeoff there, and saw that the closed door people tended to not be as relevant years later as the open door people.

https://en.wikiquote.org/wiki/Richard_Hamming

Email generally offers one more control over one's own workflow, and perhaps the opportunity to be a bit more focused, in an otherwise constantly-connected environment.

Code wizards need time on the lonely mountain to learn new spells.