SIERA.AI Computer Vision Machine Learning Software Engineer interview questions

At first I had a short chat with the CEO which went okay. This was for a remote job, so everything was online. Then I was given 2 timed coding tests from Coderbyte that I could solve using a language of my choice both of which I cleared. Then I had a Management Interview with the COO on phone call, similar to a normal HR interview (that I didnot get through). There were supposed to be 2 technical rounds (coding project and project review) after that. Normally the HR phone call is what companies have first (go over your CV, what are your salary expectations, when are you looking to join) before moving on to the coding tests and other technical rounds. I wish they had done that here as well. Being rejected at the management interview after going through the coding rounds made me feel like I just wasted a month over something that could have been decided within the 1st week itself.