I don't agree with their logic. The text is the same on the handwritten note and the email. You lack visual and auditory clues for both equally. I always use Crane's or Cartier's stationery for thank you notes, etc. rather than email. Tradition dictates my choice. The feel of paper is nice. It is cultural. I am certain young people raised on the Internet find email messages better. I am older so I stick with what the etiquette books taught me. An email is not faster if the recipient does not check their email program frequently.
Quality paper is very nice. The vast majority of my correspondence is email and I am older. There will probably be a small niche group that continues to use handwritten notes. I believe the warmth of a message comes from the language. Also, I only handwrite those short folded notes. I don't know if I am physically capable of writing 6-7 page personal letters anymore. Bad penmanship is an issue, too.
The bigger point for me is who cares? Where does the Bible mention Crane's or European stationery and emails? They opine on the silliest things. I recall a convention where the main speaker gave women cooking advice. Never serve all white vegetables. Always serve a green to look good. It is visually pleasing. If you must serve all white, add parsley on the side or a sprinkling of paprika. It makes sense coming from Jacques Pepin or Julia Child. What is religious or spiritual about parsley or paprika. I could not believe my ears.