Vray also isn't based fully on embree, although I am not sure if the Embree support isn't on by default there too.
It's only V3/V4 that have the AVX-Turbo concept and mainly V4 where it's most prominent.
By perfomance comparison I meant that I compared the ratios of my v2 and v4 xeons in Cinebench and CoronaBench. The fact that my 2698v4 ES underclocked didn't skew this ratio negatively, which means that the AVX instruction did potentially offset performance in positive way.
This is actually the argument that Intel keeps making. That despite lower clock while using AVX instruction, the actual net performance is higher.
This doesn't take into consideration that ES have worse turbos in general so the net performance is probably worse, but not as worse as pure frequency difference would hint at. The end takeaway is that frequency simply isn't everything when it comes to all the modern instruction sets.