Hmmm, I would never use such a system as for one thing - if people aren't contacting me, why should I care about contacting them? I have several 'best friends', maybe twice that 'friends', and then a bunch more I interact with sometimes, and I feel this is relatively normal. Also, I don't care actually if it's not normal, and don't feel I'm missing out on anything. That said, I'm quite the introvert and generally value time by myself over time with others.
Still, if this is what works for the author, and they feel they need to 'keep in touch', and that describing such a system helps other people, then good for them. Someone else using this system doesn't hurt me in any way, in fact if I was contacted by someone AND found out about the system behind it, my curiosity about how it worked might lead to a new deeper friendship.