Notarization is mostly a glorified malware scan. There's no Apple engineer auditing what's being sent for notarization. Even clever malware can evade notarization scans and be distributed as a notarized binary, it has happened in the past [0]
There's no better way for auditing such an app than having the code easily available and looking through it, and compiling it yourself. Which is already the case here.
After a different company detected it, figured out what it did, and reported it to Apple. The app was notarized on November 17, screenshots in the researchers' post are from December 16. That's a month of fully notarized distribution.
While I disagree with you, thank you for sharing your decision-making process: you're probably not the only one who thinks this way.
In general, would you pay for a notorised build of free software, if you had use for that software, even if an un-notorised build or the source code were available?
It depends: having it notarized is a way to show someone with a certain reputation of "Hey! This is my code, this is me, if something happens, you can kill the switch".
If notarisation requires you some kind of payment, I would be okay with you charging me some money, if I obviously find your code has a good value for me.
I read comments around here about "Well: you can compile it yourself" or "it's open source! You can check the code by yourself".
And, while all of those arguments are accurate and valid, the point is "I do not feel like it" or, a little reminder, "The Great Suspender" was an example of a beautiful open source little app to suspend tabs on Google Chrome that, one glorious day, switched hands and, suddenly, after some time, someone noticed the repository and the code from the add-in were different, and those changes were made with nefarious intent.
Luckily, somehow found out, but some people do not have the time or the will to be playing that game.
A piece of code that requires access to my camera, regardless of size (<1000 lines of code) or build, it's something I just don't put on my computer without thinking it twice.
Thank you for the tone: I hope I responded to your question :)
You may be severely wrong: I like to pay and contribute to things I use, believe it or not.
I love to buy small apps from indie developers or donate some money to things I use and I love: when I was a student, of course, things were different.
Nowadays, luckily, I can contribute and I do it gladly.
Get it notorized and ask for some money! I will gladly pay it (and I hope others will do it as well).
Awesome concept: ergonomics and/or posture monitoring is a market opportunity for heavy users.