I'm not sure that this is true.
Perhaps. But in a social context I think my point still holds true. AT followers in my limited experience don't handle fast and long strides at all, and besides, you'd be pretty lucky if you have that sort of space. Crowded, small floors are the norm in AT. The good thing about all this of course is that floorcraft is so much easier in AT.
The musicality that the leader can impart in ballroom is pretty much with tempo rubato, a well placed checked or half-beat step, and the shaping he creates with his spine (only slight - the follower does the majority of this), subtle variations in the character of the rise and fall and the even subtler aspect of breathing. There are also various line figures that can emphasise certain sections of the music but I don't like them on a social floor (I think they create floorcraft issues for others). Ballroom tango does allow more room to be creative because the momentum in the dance is checked, and you have the options of legato and staccato foot and body speed. But still not as much room as in AT because BT has no steps without a weight change at the end, as far as I'm aware (the ballroom swing dances do).
Musicality in social ballroom is difficult because floorcraft and protecting your partner from collisions is the priority, and your choice of steps, and the character of their execution, is more influenced by this than any concerns with the music. I'm certainly not as musical in my ballroom as I could be. Still working on it.
I would add that AT has cross-sytem in stepping
I don't think this will be an issue for leaders as long as they aware of which is the followers standing leg [point (1)].
Might be an issue for followers. I couldn't say - I haven't tried genuinely following in either ballroom or AT. I will at some point want to do that as I think learning to follow makes for a better leader.
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I'd also add that one thing that takes some getting used to, for me, is the assertiveness of the arms in AT leading - The security of the embrace seems essential. In ballroom there is a signal-execute-follow cycle (the leader signals his instruction, the follower executes it, and the leader follows the follower as she does so). I suspect that many AT followers would find this approach to soft.