Absolutely correct. That deleted scene fragment was finished using the budget assigned for the promotion of the film, creating trailers and such.
It's in the bonus features section, but is only few second piece of the entire deleted scene that can be seen in its entirety in the deleted section.
Or maybe it was completely finished, but cut at the last second? I think all of the stuff we saw in the Nemesis trailer that never showed up in the movie was cut at the last minute ... I mean, why would they put all those scenes into the trailer when they already knew they would never actually be in the movie? There are probably more finished scenes cut from Nemesis than we know.
As for Generations, I don't know ... I guess it depends on which point in production it had been decided to cut those scenes.