Well, it's a long story
One of the annoying bugs of Adobe Premiere is that it can't deal with 23.976fps footage. Upon export it will make it 23.98fps which is no use to man nor beast.
What I used to do to get around this was to:
a) take my audio stream and do a rate change on it
b) assuemfps(24) on all 23.976 source footage
c) edit at 24fps, export at 24fps
d) Assumefps(23.976) on exported video
e) Re-attach original unchanged audio stream.
But once upon a time, I didn't think about doing things this way - I just edited at 24fps so I wouldnt have frame drift because of premiere being dumb. Then I realised that to make things 29.97fps I'd have to either change the audio stream or remove frames... neither of which I wanted to do. This is where the idea came from.
I'll look into changefps, but I figured doing it in the telecine would smooth out the transition as much as possible.