While DAZ started out as a company making figures for Poser, that's not what they are now, and they really have no reason to make sure the figures work in Poser at this point. DAZ Studio and Poser are competing programs. The question is why Smith Micro can't seem to make current figures for their own software. Actually the question can be stretched to why Smith Micro has never come up with a line of figures that caught on.

If SM wanted to use Daz 5-7 figures they could have written the support into Poser, it clearly wasn't a priority for them.

As far as the V4 vs Gen 5 characters, I can tell you that at the time, as a DAZ user, using V4 vs Gen 5 (the first genesis generation) was a toss up - Genesis 1 is not all that realistic particularly in Facial Expressions, and didn't bend all that well. Frankly it was great for any character what wasn't human, and I still use it for that.. Genesis 2 however is far superior to V4.