I once had to do a full-stack coding task for a YC company - I think it was something like build Tic-Tac-Toe with backend validation and storage of game state. I built it, and instead of being called onsite, I had a phone call with an engineer. I expected to discuss my solution with the engineer and prepared accordingly, but they did not mention the assignment at all, and proceeded to ask me algorithm and database trivia questions. I did not get the job.