I read that. (I literally mentioned features not being paywalled in the original comment.)
If the key doesn't unlock features, what does it unlock?
Do you get a little thank you message from the devs when you enter it in? Does it add a "Supporter" tag next to your name on the app settings?
The practice exists in both software and games of adding paid cosmetics (e.g. Discord or Deep Rock Galactic) that don't change the core featureset but allow users to pay more to support the developers, so I think it's a valid question.
I was excited at first, because I thought I could still chat with friends who won't leave Discord.