That is indeed the crux of it. If you write me an inane email, it’s still you, and it tells me something about you. If you send me the output of some AI, have I learned anything? Has anything been communicated? I simply can’t know. It reminds me a bit of the classic philosophical thought experiment "If a tree falls in a forest and no one is around to hear it, does it make a sound?" Hence the waste of time the author alludes to. The only comparison to email that makes any sense in this case are the senseless chain mails people used to forward endlessly. They have that same quality.