To acknowledge that our spirits shall rise to unite with God is the most beautiful gift of Samadhi. This is expressed through the gift of breathing.
Promoting compassion, goodwill, kindness and service bring out our highest spiritual potential, Sattva (Sattwa). This positive, calm and content predisposition, is inherent to all and could be practised even without the physicality of yoga.
He knows and acknowledges his limitations so he could willingly and easily get detached from this euphoric experience. Beyond this is not wise. He needs to go back for him to share this beautiful spiritual journey.
Yes, it is the universal energy but it just doesn’t manifest so easily in a stone or a colour or a visualisation or a sound just like that.
Externally, Guhyasanas, resemble asanas (poses) but they go beyond. They defy many of the commonly accepted physical alignment principles. The body surrenders to the innate flow of the primal energy, the Kundalini.