It goes right over mine too. I just don't get it.
Like you, I agree that Samba technique is the hardest of all the latin dances, but for myself, I have never had any trouble with the bounce action: I have a very strong sense of rhythm (I'm a trained musician, and a percussionist, at that), and the "down" on the first step of a volta fits perfectly with dancing Laird's technique reversed. Hell, it's what EVERYONE does - why should I worry about it?
I do worry about you claiming that "a" is up: the beats "1", "2" may be down (sorry, Wally), but "a" comes exactly BETWEEN & and 1 or 2 - and it is the "&" which is "up". The "a" step is right in the middle of the flexing/straightening movement, so actully coming "down" too. That is why we have to overlay the 1&2&1&2& bounce with the 1 a 2 1 a 2 step pattern, so that we get, in combination, 1&a2&a1&a2.
The beats go 1/2 /12 1/2 1/2, but the steps 3/4 1/4 1 3/4 1/4 1 - unless of course we have a QQS - and we ALL know what that means, don't we?