Not necessarily: it would depend on what Dreamworks' requirements have been up to now as to the current state: obviously, they use volumetrics, but almost all their stuff is CG and not necessarily photo real, being more artistic-driven.
That fact might have allowed them to take short-cuts.
I'd guess that the volume rendering in MoonRay is pretty top notch considering Dreamworks was also responsible for creating OpenVDB. Furthermore, while their characters and environments are often stylized, watch a few minutes of How To Train Your Dragon 3 and you'll see their volumetric rendering is stunningly believable.
MoonRay likely has the best volume rendering in the world, certainly that's open source.
Only Weta's internal renderer is in the same league.