That is intriguing. But if those objects didn't fit the hypothesis, they would have changed the hypothesis to account for it.
I'm not trying to pour cold water on this - the Nice model does work well with five giant planets, not four. And the odds are that we have larger objects than Sedna to account for that haven't been found - at least one Mars-sized body is likely. Another giant planet isn't entirely out of the question, although a Jupiter or Saturn-sized object "relatively" nearby seems to have ruled out by current observations.
But it may be that we're seeing the result of many wild theories, and this is the only one that survived the data we have. Future data may disprove it. Still, we have enough oddities in the outer solar system (Kuiper cliff, elongated orbits of some of the dwarf planets) that it's obvious our current theories have some holes in them.