What I find curious is that the entire article seems to be framed in responding to the needs of a single user of the app — the author themselves.

Yet the app is published and has a great App Store review score of 4.8 with 170k+ reviews, and same score with 35k+ reviews for the Watch.

How does the author get feedback and respond to other customers? Or is this simply scratching one's own itch demonstrating its usefulness for others once again?

Most likely both :)