I'd like to know what the criteria for advancement is, for Martial Artists, I refer to natural. I mean, it's clearly not something like "reaching the limit of the body", because the MC can become an EH and an MH without having reached such a limit, and there are many PHs with stats below 5k. Nor can it be something like accumulating the maximum amount of Inner Energy, because IE is based on stats.
As for Xiantian. In Yang Chen's book, he says that less than one in ten thousand advance to Xiantian and that "enlightenment" is necessary. But there are so many random Xiantians around the game and most of them just seem like average EXs, none of them seemingly top 10 absolute geniuses or close to it. It's hard to imagine that such people have reached enlightenment while Yang Gan and similar have not.