Your middle two paragraphs were what I was trying to say too: this should probably be a thread in its own right (and it’s been touched upon a fair bit) but I find partner-familiarity and TA-dancing-quality to be mutually-antagonistic... music that I know and feel danced with a blank slate as a partner – if I know that her dog has a bowel complaint, that she watches TV and likes mushrooms etc, then that will get in the way of the pure expression of the music... and by the same token, if I know that she loves philosophy and painting, I will find it harder to find the necessary (for the dance) emotional detachment.
Maybe that’s just me (and is unique to TA, for me).
I find that to be a slightly peculiar attitude! For me, when I dance tango, it's not simply about the expression of the music, but also about the connection I feel with my partner. Through that connection we are able to negotiate our interpretation of the music together, with the end result being something unique and special, different from what either one of us could have produced alone. Intentionally creating emotional distance seems like it would sabotage this process, and very possibly impose limits on the quality of the dancing itself.
I find that learning details about the person I'm dancing with allows me to make it a personal experience, rather than just a mechanical series of movements done to a complex metronome. In any case, to a certain extent, it's unavoidable: as soon as you start interacting with someone, you are learning all kinds of details about them, everything from their physical appearance to their moods, even their personality... and that's without them ever having to say a word.
Anyway, I could be wrong. These are just my musings on the subject.