Yep, my PRM is an iOS Notes folder called People, with a note for some people I want to remember facts about. In particular what some like so I can use the list to make gifts. There is also a "debts" notes. I’ve been using this system for a few years and it works well.
The tooling you describe isn't relational. Furthermore, Monica has found great success in helping users with social challenges, maybe with ADHD. The workflow you describe isn't an ideal solution addressing that challenge.
I would say it's more ideal than Monica. Monica is a separate app from the ones you usually use, using a separate database, with more latency before first input, and more button presses before you can actually store anything. These are all bad features if you're trying to augment short-term memory. I'm not a fan.
(Moreover, Contacts is absolutely relational, in any sense that matters. There's a Relations field. It's stored in a sqlite db.)
https://superwishlists.com.au - it's not open to public registration yet, but it'll get there in the next few weeks. It solves the problem you've outlined and a bit more, whilst being free in every sense.