There are times in life where sometimes you just want to built something amazing, and you don't want that process hindered by those who only work 9-5. I personally worked this way until my mid 30s, and the best companies I was a part of were those companies where most of coworkers were young, smart, and passionate about what we wanted to do, our lives had no balance because we all obsessed over what we were building.

To me, this is likely who they are looking for, and why they are unapologetic about putting it there.

Typically founding team means a stake in the company, and that your efforts can shape the company and you have a voice at the table.

I'd say everyone could benifit from working on a passion project like this at least once, but that's just me.