Noom interview questions

During my process I had 2 phone interviews. 1 coding and one "problem solving" (similar to system design in FANG companies but focused more on algorithmic complexity than regular system design). It seems like the questions are standardized and all interviewers ask all candidates the same questions (at least in the first 2 interviews). I think generally that's good and I actually liked the questions, I think whoever designed the interview questions definitely knew what they were doing. One "+" that I would give the company is that when I got the rejection, they also provided an explanation for the rejection. The "-" that I would give to the company is the interviewer evaluation skills. I was rejected because my solution was "sub-optimal". My impression though is that since the questions are standardized, some interviewers sadly can't evaluate properly the solutions that deviate from their predefined standard solution. In my case, my solution is provably optimal since its run time is pretty much limited by I/O speed and my solution runtime would be the I/O time with slight overhead and would scale down linearly with the number of machines that are thrown at the problem (for the given problem, clearly the lower bound on the runtime is the time required for parallel scan of all the data once).