Its possible you’ve run into a bug that was present in Krakatoa 2.0.1 that caused Phoenix FD to appear to have no particles when rendering a sequence, but it would look fine when rendering a single frame at a time. Please try installing the updated build which can be found on this page: http://www.thinkboxsoftware.com/krakatoa-downloads/builds-beta/
Would you be able to post a scene file that shows me the problem? I must be doing something differently. You can also send it to darcy AT thinkboxsoftware DOT com.
In the top right corner of the post there should be an edit button, like this:
I assume you are asking why we would load the Phoenix particles directly instead of using a PRT Phoenix object that points at what you want to load? Or perhaps you were asking why we don’t create particles using the Phoenix voxel field. The gist of it is that the Phoenix support was added quickly shortly before release so it wasn’t able to be fully fleshed out like the support we added for FumeFX ages ago. We have a TODO list entry for making it better.