Hello Aham That,
I share your observations, but don't know exactly if energy is lost or not. The original advice here is to stay ahead of anything that could be called an orgasm, although if there is such a sensation that doesn't really peak (ex. vajroli) it would be exempt from that. That method does feel like a sort of peak, but it can be repeated when stimulation becomes overwhelming or even before that, and it helps keep the overall sensitivity in balance most of the time, whether that means increasing or decreasing it.
In many ways, I tend to think of this method as a sort of over-exerting the muscles in the region, which helps dissipate the energy internally by the forced relaxation that results afterwards. At least one of the tantric texts translated by Lilian Silburn mentions the muladhara as 'triangular' which if turned upwards directs its energy into the sushumna. This method, which is quite intuitive to do, might help that greater process along. Either way, if there is a drain associated with it, in my opinion it seems minimal, and helps to extend the tantric practice along, which comes with its own benefits.
