This energy transfer was a simple training method which the Black Coats possessed, specially designed for the Dao Yuan class.
In reality, someone capable of inventing such a straightforward training method probably wouldn't be someone who had a simple role to play.
According to Xi Fei's words, the training method which Lu Shu possessed was called the mysterious matter cycle and he was needed to train his own body.
It seemed like the first step of the Daoyuan class' method was quite similar to the celestial map - and it was to train the body first before working on anything else.
