Slide control works on both entry and exit.
It isn't so much "extra traction control" as it is changing the parameters of traction control. Normally, traction control will attempt to prevent a slide. Slide control adjusts the parameters to allow a degree of pivot, or kicking out the rear. Instead of stopping wheelspin right away, it sets the TC to talk with the IMU and allow a few degrees of pivot. Slide 1/2 are essentially levels to it, 2 allowing the rear to kick out further than 1.
It also talks with ABS, such as your example. Jam the rear brake on entry with slide control on and it will tell the ABS to allow the rear to kick out to a certain extent. What I am not sure about is how it interacts with ABS 1 (no rear ABS), if it intervenes still or doesn't come into play at all.
It is basically designed to solve the problem of guys wanting TC but also wanting to use controlled sliding to steer the bike on exit. Many TC systems intervene too much, so you either have to keep it on and sacrifice sliding or turn it off/down significantly and be able to slide, but lose the safety net of more aggressive TC. Slide control allows you to have your cake and eat it too.
