Asana Business Strategy Associate interview questions

Phone screen with recruiter and Phone screen with Hiring manager, about experience and some generic questions. I was called for the onsite set of interviews. This process was 2 weeks after my phone screen because the team was unavailable. Fair, it was my choice to wait. I was give a case study for presentation. The on site was almost an entire day process with several interviews with the team. What made me feel violated here was that both the business case and the interview questions were all about the current problems at Asana and the candidates spend a LOT of time trying to solve this. I felt like Asana does these rounds of interviews to source ideas for their process. Although the interview was very professional, the reason provided for not moving forward seemed non substantial. I was told that there would be challenges in cross functional collaboration. How does one access that? I set up a call with the recruiter to discuss why was this decision was made. All I heard was that there were no "red flags" but did not have a solid reason or explanation. Should there be an NDA that the company signs too saying that they will not be using the ideas 'sourced'? Not moving forward with a candidate is perfectly fine and totally the discretion of the hiring team, but this is first time I felt violated after an interview process.