So, the issue is that,
verbal rules aren't worth the paper they're written on (misquoting Samuel Goldwyn). It's a
convention, not universally accepted, or even known. Etiquette in your locale most likely differs from etiquette in Europe or Asia. It's even different at other milongas. No rules posted. No enforcement.
So, the codigos, as an extrapolation from what someone thought was a
good idea in BsAs may be meaningless (as noted in other threads). It's a myth we construct about [better] past times in another place. Maybe some got written up in a book or post that you read?
If you travel to other countries then you observe and learn the 'rules' people apply there.
It's that old film theme of respect.
You disrespectin' me? And what do you do about it? Knives out? Fume? Never attend again?
AT is more than just a dance. It's about socialising within the norms (codigos) of that locale. It's about men (as leaders) asking women (as followers) (or vice-versa) to dance - in an intimate connection in a managed environment. Like any other situation (work, study, exercise, gym, shopping) more can develop, but for most it's just about the dance - but some will always try to explore. Is it different from the woman away on business alone in a hotel bar getting hit on? Or the guy in a relationship, but away on business, doing it?
If you've got a secure relationship, it's not a problem. Someone requests a dance with my wife as soon as we arrive? So what? He's a jerk if he knows us, or an ignorant novice if not. Or maybe the last dance (unknowingly)? Well, we're not going to let it spoil our lives.