Your argument is that using coding tests under interview conditions is bad because a poor interviewer will overweigh it in their assessment. But the same applies to everything that takes place in an interview. Some interviewers will make up their mind on the candidate's handshake, so it's probably not fair to have handshakes in an interview. Others might place too much weight on the vocabulary and language an interviewee uses in answering questions, so we should probably not let them hear the interviewee speak. And asking candidates to write code risks the interviewer placing too much emphasis on the interviewee's ability to demonstrate their coding skills, so we should prohibit that too.