I'm not sure exactly what your disagreement is. I agree interviewing shouldn't test a single skill. I also agree you can get better at interviewing. But I still

I'm not sure exactly what your disagreement is. I agree interviewing shouldn't test a single skill. I also agree you can get better at interviewing. But I still think the interviewing process you use is more important than the skill of the interviewer. I have done a similar number of interviews as you, and I've found very little correlation between performance on FAANG style interviews and performance on the job.