Here you've got me. ;-)
When I'm speaking of Tango, I'm refering to argentine Tango.
Ballroom Tango of course is Tango, as it is called Tango but is it a totally different dance although it developed out of argentine Tango in the twenties.
Although Tango is a highly individual dance, there are of course some general rules:
1. The posture: regardless of open or close embrace the couple form a triangle if seen from the side. Means: chests are nearer then feet in order to allow free hip-torsion and movements of legs
2. The rule to keep the knees together and walk on one line.
3. The movement of the upper body initiates the movement of the hips and legs.
4. Out of 2. and 3. results: the movements of the pivot of which results every ocho and turn.
5. There exist some common structures like for example how to turn around the man. You know: The molinete (back-side-forward-side). But these structures may be altered also. A man may lead only sidesteps around him or back- and sidesteps...
6. One must be able to lead every single movement without having to rely on steps. Of course many a beginner will dance steps without beeing able to lead them, but they must be "leadable" in principle. A movement which is only initiated and then goes on automatically and can not be led or stopped, for me is not tango-like.
7. steps are only examples and not binding. The emphathis lies on improvisation
8. So one of the main principles in Tango is that there is no standardization. Even techniques may vary: there are people who walk only on their toes, other set all the foot. Some people lead only with their chest, others use their arms...
This means: for me, ballroom tango is not argentine Tango. The posture (contact with hips, chest apart) is opposite to the one in AT, steps and techniques are well defined and binding in order to compare the couples to each other. Improvisation is seldom.
But of course one may dance a promenade in a Milonga. One may even dance ballroom at a Milonga if one is able to move without disturbing the other couples. And if they dance a promenade according to the general rules of tango (in the right posture, leading every single movement, without having to dance it right to the end of the step) this step (the promenade) may be even integrated into Argentine Tango, because Tango does not exclude particular combinations of steps to the front, back and side.
And most of the Milongas I visit would not make fun of the people dancing ballroom... unless they start throwing their heads from one side to the other and carrying a rose between their teeth. ;-)))
So, if you once come to my Milonga in Germany do not hestitate to dance as you like.
byebye