I definitely agree that it’s real, but I’m unsure about the notion of it being practical solely through sex. It was my understanding that Kundalini is a separate practice, involving things such as Kundalini yoga and breathwork, feel free to correct me.

Yes, there is this possibility to use breathwork (Pranayama) to energize the spine, but only works for the first vertebraes in coccyx region. To progress further you need to use the energy transmuted from practicing sexual alchemy. The awakening of the Kundalini means that each vertebrae must be energized (33), and this energy is also used to activate your chakras. With each activated chakra a new sense is unlocked, we have 12 senses and only 5 are available for the majority of the population. Activating the 7 chakras gives you 7 new senses: premonition, telepathy, astral projection, intuition, clairvoyance, clairaudience and polyvision. A good source of information about this topic is the book Perfect Matrimony from Samael Aun Weor.