I’m glad I could help you understand something a bit better. As I said, that was written to my boyfriend, and he tends to inspire me to all forms of eloquence.
Yeah, one of the major factors about d/s stuff for me is that it tends to involve one person slightly dissociating from some part of their own physical or emotional stuff in order to create a larger, different, or particular effect for the other. (This may not be very coherent; I don’t think I’ve ever verbalised this before.)
This can lead to some very intense stuff if done right, with the ‘dissociated’ emotions and urges expressing through the channels that are appropriate to the interaction and heightening them, and the expressed things getting a very focused treatment because all the energy is going through them, not a broadband. On the other hand, if it goes wrong, it can get very, very strange and sometimes messy, with the detachment winding up in places it really doesn’t belong.
And a slightly obsessively geeky bit of my brain wants to say that it’s like taking a phase as a specialist wizard in D&D for me. Sure, you lose an entire school of spells, but the spells of the chosen school come out significantly more potent. And unlike being a specialist wizard, one can stop doing it if one doesn’t feel like it.
(I don’t know if the detachment is universal or anything, but it’s definitely how things wind up for me, and I’d guess that it’s some of how it works for your friend from your descriptions above. One of the things that I’ve done with this particular corner of my mind is feel out where some of the detachment goes in good directions and where it goes in bad, messy directions, so I know what sort of situations I’m comfortable in.)
I feel like noting that one of the things that I can successfully detach from as a sub is a feeling of needing to be perpetually on-guard, perpetually ready to deal with crisis or the like. I’m very, very control-freaky, and it can be horribly draining of my energy, mental and emotional. When I go sub, one of the major benefits I get out of it is that my dom is handling that sort of thing for me – I’m safe, I trust him, I don’t have to worry about that, I just have to worry about what he’s doing and what he wants me to do. If I need to be protected, he’ll protect me, and because of the trust dynamic, I can shut that entire part of my brain down for maintenance.
(And, to your OP, there may be something of that for your friend; I wouldn’t be surprised if a goodly fraction of specific-context submissives were very dominant personalities in other parts of their life.)