The answer I got from Rouvy support was this:
"To compare Zwift resistance with Rouvy - 100% in Zwift equals 60% in Rouvy.
You can try it, if you ride in Rouvy in Training mode, go to Settings and set the reality level at 60%.
The video speed depends on your speed. If you ride certified routes, then the grade of the route should be the same, as you see in the video. Sometimes the gare [sic] is adjusted to enable smoother ride."
I tried again today as I had the reality level set to 100%. I reduced it to 70% (the dropdown does not provide a 60% option on apple TV). This resulted in a MUCH better ride with the start and end of slopes seeming to be much closer to the visual expectation and the transition of slope segments. So - it seems that "reality" is ~ 70% of "reality" .... Rouvy did not define their "reality". Depending on how you read the comparison to Zwift - either Rouvy is more real than Zwift or Zwift's virtual world is more real then Rouvy 
. All I can say is that for me Zwift at 100% feels close to real and Rouvy at 70% feels close to real.
@jmess - the behavior I was experiencing was that the effect of the slope segments was not happening as you went from one segment to another. It was either delayed or happened too soon (it seemed - depending on speed) and by a long time.