I would imagine a significant part of how complete a simsense interaction is would be the source of the simsense information. For example, you make your persona look like a dragon (excellent example, BTW). Unless you have applicable simsense data when you create the persona, or it comes with the icon when it is purchased rather than user created, then your persona would not give you the actual feeling of being a dragon. Of course that simsense information would be available and could be integrated, but would still be limited by the data. Did the dragon making the simsense recording eat food during the recording? Then you know what it is like to eat as a dragon. If they didn't, having the recording won't let you know what that experience would be like. The dragon sex question would be same. :-) I also think that would be where "holes" would appear in any simsense experience. Any specific activity that hasn't been experienced and recorded by someone in a simsense rig would be missing from the simsense data, and so the experience would have to be extrapolated from available data. I should expect that there would be a lot of extrapolation given that most simsense consumers won't be doing the exact same things as the simsense recorder did while recording. Right off the bat, they have a different body so the recording would have to be adjusted to make sense for them. A simsense user could also consume simsense in a completely passive fashion, making no attempt to make it seem that they are the one having the actual experience. Such an experience would be a perfect rendition of what the recording contains, but would also absolutely be obviously someone else's experience.
I like the idea of "the run that wasn't" simsense. It would be a huge challenge to the computers involved to fill in all the information not available as regular simsense recordings, and to do so to a degree that it couldn't be noticed by the users. I imagine that when simsense users want to feel like the simsense is real, they get pretty close to what they are looking for. I don't think that it would normally be able to fool most people, under normal circumstances.
I also believe that BTLs, while intense, would be wildly obvious as synthetic experiences. A BTL user would not feel like the BTL has any real bearing on what a regular experience of the same type is like....but then, that's the point, isn't it? :-)
I will have to look at the simsense book mentioned however, as my analysis could be completely out of sync with the authors intend.