It is indeed perplexing ... as others have pointed out, there are likely only a few reasons why RVX "voluntarily" pulled out.
Either the data upon further and deeper review was miscalculated (errors), or deemed unworthy of late breaker status, and RVX was allowed to "voluntarily" pull out for face saving? Unlikely scenarios in my mind, as this data has probably been studied and scrubbed for months by scientists, statisticians, and computer algorithms, and likely previously presented to regulatory for review (BTD filings?).
I don't buy in to speaker unavailability, if the data is good and worthy of presentation, any number of people would be able to run through the slides and discussions in a virtual presentation.
Or, the NKF has limited strategic value now, as a venue or timing? ... at this point. But, if the data is good as we believe, and was deemed worthy of a late breaker podium spot? ... why not get it out there after this long wait? Can't think of anything but "good" reasons, "IF" this is the case.