Yes, Lee, that's the gist of it.
I can't talk from any knowledge (yet) because my aircraft is still a twinkle in my mind's eye but, from what I've read here and on other forums, is that wiring up to an EFIS (an MGL unit in my case and the one I've read about) from the PAW involves transmitting the data using a USB wire. This is great in that it gets the PAW information to the EFIS BUT, apparently, the EFIS gets ALL the PAW information and there's no facility to filter that at the EFIS. It would seem this is also the case with some of the nav software, such as XC Soar. I must explain that I have never actually seen this in action but it is what I've read and I'm sure someone will correct me if I'm wrong.
What I thought is the same filters as Sky Demon, for instance, could be set in the PAW instead; that way any kit without the filters would be able to enjoy the current facilities enjoyed by those that do have the filters. It might be that some prefer to set their filters in SD and that would be fine; they'd just leave the PAW ones raw and adjust things on their iPad (or whatever). I intend to have SD on an iPad with PAW and, in addition, PAW piped to my EFIS....just because I can and I like gadgety stuff like that :-) It would be really nice to be able to exclude Speedbird 268 from my screen at FL350 because I get enough of that crap at work and don't really want to see it when I'm tootling around enjoying myself.
Again, having not seen it in action, I cannot comment intelligently on the transmission of PAW data along a serial wire but I can only imagine that reducing the amount of unnecessary/unwanted data before it travels down that tube can only speed things up.
I hope that explains my thinking but, if not, please don't hesitate to ask what the heck I'm going on about