It's relevant to the idea that if an email enters Google, it's probably accessable to the NSA, even if you delete it. I was directly responding to:

"is it indisputable fact that the NSA has all your email, or, is it more like, we can't be sure what they do and don't have access to"

They don't need to have second hand copies of the mail when they can just tell Google to give them access.

"implement a webmail service without storing emails." is not relevant to anything I said.