In Generations, both Picard and Soran physically disappeared as the nexus ribbon passes over them, so Kirk's body wouldn't have been just floating out in space after his consciousness, his soul, was taken. Now that doesn't mean tha his body was transferred into the nexus, but I think that's exactly what happen.
Something had to be able of leaving the nexus and being physically present in the "real world" again when Kirk and Picard left the nexus. This is why Guinan could not leave the nexus with Picard when he asked, her pysically form, her body, had already left.
When in the nexus you are either motionless and all your experiences occur in your head, or you are actual experiencing all the nexus event with your own physical being.
One thing I wonder is, is Soren still in the nexus?
How does that work if it is moving through space?
The mouth, the opening of the nexus is moving through the galaxy in real time, Picard was able to return to Veridium III because the nexus had been there, so maybe Picard couldn't have instead exited the nexus on Earth days before and saved his bother and nephew if the ribbon had never been there.
You can only get off the bus somewhere on it's route.
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