This is less about the interview process and more about the application process more broadly. Mathematica ghosted the summer fellowship applicants, not telling applicants when they had made their decision. The application required an individual research statement beyond just a CV and it’s unprofessional to not notify applicants. Mathematica had been one of my top choices for a career after graduation, but since this happened I’ve been more heavily looking into other options and I’ve spoken to others who feel similarly.