EnOcean Software Engineer interview questions

Had a short initial interview with hiring manager. Then I was assigned a coding task which stated 6-8 hours to complete (I found that quite optimistic) and was given a week to submit. That feels like a student submission. How can a full time employee finish a 8 hour assignment in a week time? Spend your entire weekend to work on it away from family which is a big sacrifice which I did. Then I reveived a single line response next day thanking for submission but the team did not pick you. And that was it. I was upset and asked for feedback politely. Never heard again!