Technology

Yes and no. It's not a solved problem, but a worked around problem. Diffusion models struggle with parts that are especially small and would normally have to be done with precision to look right. Some tech does better on this, by increasing the resolution (so that otherwise smaller parts come out bigger) and/or by tuning the model such that it's stiffer in what it can do but some of the worst renders are less likely.

In other words, fine detail is still a problem in diffusion models. Hands are related to it some of the time, but are not the entirety of it. Hands were kind of like a symptom of the fine detail problem, but now that they've made hands better, they haven't fixed that problem (at least not in entirety and fixing it in entirety might not be possible within the diffusion architecture). So it's sorta like they've treated the symptoms more so.