They are both correct. The first article you referenced does not explicitly state that the energy facilitated through the mantra "Sah" goes to the heart, but it does. Elsewhere in the literature of Samael Aun Weor he explains that it is necessary to send the transmuted energy from the brain, from the solar "Ham" to the heart, through the lunar "Sah." Does this answer your question?
Joyful in hope, suffering in tribulation, be thou constant in thy prayer.
Benedictis, qui venit in nomine Domini. Osanna in excelsis.
"Blessed is he who comes in the name of the Lord. Hosanna in the highest!"