Yes, it's fundamentally unfair to those interviewees who don't cheat. And the process is broken. However, the conclusion this person reaches - we must conduct these broken interviews in person so the cheaters can't cheat - is the wrong one.
Look at it from the point of view of the hiring company now, not the interviewer. They got a person who was good enough (based on the merits of their actual work, not interview performance) to subsequently get promoted. So, hiring mission accomplished, end of story. They may not have found the very best person for the job (very subjective and unknowable anyway), but if the process didn't result in an under-performer taking the job, the process did not fail. And, importantly, there's no reason whatsoever to think that if no cheating was allowed and a different person took the job, that they would on average be any better.
Look at it from the point of view of the hiring company now, not the interviewer. They got a person who was good enough (based on the merits of their actual work, not interview performance) to subsequently get promoted. So, hiring mission accomplished, end of story. They may not have found the very best person for the job (very subjective and unknowable anyway), but if the process didn't result in an under-performer taking the job, the process did not fail. And, importantly, there's no reason whatsoever to think that if no cheating was allowed and a different person took the job, that they would on average be any better.