Well I am not find of his method, especially about doing a classification of people you would call friends. This is something I would hate to do and would hate feeling others put me in a drawer.
On the other hand while local friends can be easy to reach, invite
or bump into randomly maintaining long distance friendship is a lot harder to do and require actively looking for that relation to not die. It is ok not to talk to friends every month when they are living far away nor does it diminish your feeling towards them and the pleasure you would have to meet them even if it takes 10y to do so. However if you are not actively maintaining a relation, and that requires some additionnal efforts as it is not natural to reach for people you aren't bumping into every other week/month, you might simply lose trail. It is relatively easy to reach to someone who has social media accounts under his own name and never changed phone number. It requires a lot more of detective work to reach out to people who aren't active on social medias. I have lived in several countries and I had to resort to use linkedin to get back in touch with some of my friends and it can took months for them to reply as most people don't even log on linkedin on a regular basis unless they are actually looking for a job. Some of them I lost complete trail as I couldn't find any social media account either.
So automatising your own reminders and force yourself to talk to people you might not reach out on a regular basis, because your local social circle already keeps you busy a lot, is not necessarily a bad thing, even if it feels forced.