There are roughly two types of physical technique cultivation: one emphasizes rigid strength like a sturdy bridge and horse, while the other involves supple strength like a golden snake entwining.
Eventually, both paths converge at the same endpoint where toughness and softness are integrated, but in reality, these are two distinctly different paths from the beginning.
Xiehe has never seen a cultivator of physical techniques with a strength that is both rigid and supple; even those few saints who achieved the integration of toughness and softness merely displayed a degree of toughness within softness or vice versa.
And indeed, this was the case for Tang Luo too, since although he could control his physical body with Spiritual Power with an accuracy that other cultivators wouldn't dare to dream of, his style of physical techniques was still primarily rooted in rigid strength.