I'll offer my opinion on this one.
Firstly, he is a stud of a grappler. Life long practioner, and forged in a volatile hell scape of poverty, violence, and backwards ideology.
Secondly, he has a size edge. There's atleast a short list of fighters who kind of bullied their divisions by virtue of being able to make weight, but on frames suited to higher weight classes. IIRC, he cuts like 25, 30lbs of weight to make 155.
Lastly, he will always have a mental edge over his opponents. There's also an air of invincibility about him, that all of his opponents are acutely aware of.
I wouldn't consider him the GOAT, yet, but relative to his weight class, he probably will be. Perfect record weighs pretty heavily, imo. I'd like to see him get through a few more people first, and face another wrestler of his caliber.
Having said all that, I'm just not a fan of his beliefs. I'm sure if you had a private conversation with him, as part of his inner circle, and raised the issue of homosexuality, jews, women his replies would be apparently troubling. That's not really relevant, but I'm putting it out there anyway.