When I run the bend,
After about 80s gone I lean slightly into the bend and stay close to the lane – at the same time I start to turn my right shoulder towards the finish. As I get further into the bend I lean a tiny bit more and straighten up accordin to bend becomin the straight
This is kinda how I coach it as well.
To answer the original question, the 'whip' or 'slingshot' effect that many people (especially track announcers) talk about is not fully based in science. There is certainly some tangential acceleration for a couple steps but it is more of a perception than anything else.