In my experience, Hong-Sau is not about controlling anything. It’s just paying attention to what’s already happening, which seems to be what happens in Kriya in general (which is essentially the same as Vipassana). In Vipassana, the attention naturally goes into the spine.
But in terms of self-realization: that’s a strange goal since there is nobody. There is no self to realize. There clearly is libration but it’s not for anyone, not of anyone, nor is it about anyone. It’s clearly what is already happening. How can what is already happening be a goal?
I got Kriya first from Ananda and then a different form from a direct disciple of Lahiri Mahasay’s son (or perhaps his grandson?) in Varanasi.