That's not quite accurate.
Taking your advice, while watching one of Vai's rundowns this popped up…
Vai uses the Synergy units for his main guitar sound, the FX3 to control
everything and provide his effects along with Amp+Cab modeling in the FX3 for the bass and 12-string in the Hydra, as seen in
this screenshot…
View attachment 115477
and
this shot…
View attachment 115478
He also has multiple FX3s, one in his live rack, and
two in this studio…
View attachment 115479
and, being that he is a pro, he likely has another rack that acts as a backup. And, because he tours, it's reasonable to think he probably has one for his alternate touring rig(s), though, like many other acts, he might have scaled those back or might put something together from his studio gear when he needs to. And, because he has multiple studios….
It looks like it's safe to say that, while he's not using it primarily for modeling, his rig and show wouldn't function without the FX3.
It's also interesting that Dante Frisiello and Phillip Bynoe who are touring in his band use Fractals for their modeling and effects. Vai, being quite on top of the sound in his band must have approved of their sounds.