It doesn't matter because they show the images to multiple people and even shift the images around. If a square is only halfway there some people will click it, some won't and this way you can generate some sort of heat map which is all you need to label your training data.
There is very likely some step to sit on 🤣. To empty the water you just need a hose and do the same trick people use to steal gasoline (or a pump if you want to be fast and fancy).
They won't open source it because the rust code is very likely a joke. They are proud of just using two dependencies, don't know that their "statically generated" stuff is actually called server side rendering and are hosting this stuff on a fuckin laptop.
It's probably a project that will teach them a lot. But in practice their implementation is worthless to everybody else because they are obviously completely inexperienced.
That said, that project is likely not worthless to them because they will probably learn a ton of stuff why it's hard to build a search engine.
And now everybody together... C O E V O L U T I O N