i don't know if it's true but kechari stimulates the pineal gland (third eye) in a big way, and that gland produces melotonin and this substance is concidered as a powerful tool in helping our amune system and like juice for the brain to keep it fresh.
i don't see how it stops the amrita from dropping. If a fluid was dropping from the sinuses it would still drop with the tongue in kechari. For me the difference is energetic. There is a different feeling or state of conciousness that come from practice in kechari than without. It is like there is a glow in the head. I never felt a fluid drop except for when trying to penetrate the sinus holes with my tongue and causing some fluid from the sinus to flow, but this was not stopping but rather stimulating that fluid and it doesn't happen during pranayama or meditation. Not sure if that helps