From what the technical committee was saying, they were watching "DVDs" of past Tango Romanticas, and my impression was that they found few couples that did the rocker correctly, or to today's standards.
I was looking at some Tango Romanticas from 2010 Olys, and the step is unclear at best from both V&M and D&S.
While the LBO exit edges seem correct for both, the entrance edges are not clearly LFO for either couple, but rather, LFI or Flats at best. I can see where the technical committee could look at such high caliber dancers as V&M and D&S and their inability to do this turn correctly as a reason to exclude it from the keypoints. Most couples would get no higher than L2 on the Tango Romantica if they kept the rocker as part of keypoints 3 and 4.
Of course, if couples were forced to do the step correctly to garner levels, more and more couples would focus on doing the step correctly, so I understand the argument for keeping it as well.