1st step in the interview process is having a takehome. No interview or call with HR.
You have a generous amount of time to complete it. They perform 'tests' that take up to 48 hours for them to tell you your results.
However, I believe that they completely disregard the takehome results and just choose the best resume.
Given that they are citing 'compliance' reasons for not discussing what could be better, instead of doing the correct thing and wanting engineers to improve, you should avoid doing this company's interviews.