Interesting.
Personally, those lines are blurred for me (although you probably just see things with more clarity than I do)
I don't feel the need to be humiliated dressed as a female (in fact I am drawn to beautiful women holding the upper hand), it's more (as you say) that sissying up renounces my masculinity (who I am in the outside world) and the more pronounced that is, the more exposed and vulnerable I am
Whilst they have the implements and apparatus to (physically) contain me at the Fortress, I'm a fairly big, strong guy - I find it far more effective to strip all of the masculinity away (and provide it themselves) to achieve that scared, vulnerable, gurl inside that doesn't need much coercing to degenerate into the wanton slut whore to be used, broken and discarded by my Mistress
p.s. if you haven't tried this, and are interested - the Fortress is DEFINITELY the right place to come for that