"M4 comes into C4D fine from poser using an importer and works just as it does in poser using an importer.
Poser fusion also works fine with C4D.
.."

Hi no offense but you say "fine" because you are clearly someone who only renders stills.
I too use the well crafted interposer pro Plugin

But try creating an animation within poser
using posers IK on the feet
bring it in to C4D via IPP and try to make any Adjustment to it in C4D and watch the result.

Create a Dynamic Cloth animation in poser
now tell me how to render the Cloth sim In C4D Via IPP?? or poser fusion.
or a  poser Dynamic hair simulation.

but C4D has a Much better cloth engine than  poser anyway right?
OK take any of your poser Dynamic clothing items and use it on a walking figure in C4D with Maxons cloth engine show us your result.

yes you can conform Clothing items right from your runtime  with IPP just like in poser..GREAT!!

Now Accidently leave C4D modeling tools in polygon Mode and wake the next day after a 9 hour  overnight animation render to find your naked figure has Walked out of his clothes back on Frame 2.

Bring in your animated  poser fusion guy
and Attach a camera target to him and see if it tracks correctly just as it did in poser.

Do a simple poser physics simulation of james knocking over a stack of boxes.
import the save scene into C4D and carefully watch the boxes magically re-stack themselves randomly throughout  the animation.....and the same for vue

My point here?
not to slam poser itself or Roberts Amazing plugin.
In fact there are tedious workarounds for nearly ALL of the Glitches I listed above and I am not complaining.

but it does prove  that ,Like DAZ&Genesis,
you will only get true 100 percent functionalityof features within the program for which they were written  no big Surprise here.

Cheers

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