No existing Poser/DAZ figure I've seen so far is even remotely realistically sculpted or rigged.

Partly because the creators simply lack the necessary skills, partly because more sophisticated rigging isn't wanted as it may interfer with easy cloth creation, partly because the time and work needed are simply wasted on the average Poser/Studio user who prefers stylized prettyness over photorealistic accuracy.

But at least in the hobbyist sector, the alternatives are even worse and tend even more heavily towards a stylized videogame aesthetic.

And apart from the actual animation tools, with weightmapping, extra bones and JCMs, Poser's rigging is just as capeable as any professional CGI rig is.

That means, if you are willing to invest the time and have the necessary skillset, a truly photorealistic rig with "working" muscles and realistically "soft" deformations would be no problem in Poser or Studio.

Of course nobody would ever support such a figure nor even remotely reimburse you for your time, but technically I see no problem as we finally have all the tools needed at our disposal.