The Xiantian Physique was a type of an acquired physique. It was, in a way, the most accessible and obtainable physique that had one of the lowest requirements.
It didn't need someone to have a special luck, or belong to a certain line of experts. All it needed was that one cultivated the body tempering realm all the way to the peak of the thirteenth stage.
Once that happened, their bodies would reach a state where it could be reconstructed.
The newly formed body would be the ideal for cultivation and would have a far more stronger foundation than nearly any other person. Not to mention, having a Xiantian physique was the baseline needed for one to continue onwards into higher levels of body cultivation.
One could say the Xiantian physique was a gateway to becoming a true expert, since it didn't exclude anyone. An expert could even have other physiques and bloodline along with the Xiantian physique and there would be no issue.
