Okay, then 'xplain this…
On Xtri it lists the bike setups in the pro rack for IM Florida. If ever there was a course where a disk is a no-brainer, that would have to be it. Presumably any pro ridding Zipps is free to chose between 404 or 909.
On the mens pro rack were 11 sets of Zipps, 2 of these were dual 404 setups. On the womens rack, there were 7 sets of Zipps, 4 of them 909, 3 of them 404.
While disks are the clear majority, it is certainly far from unanimous.