When I think of sliding, I think of going in one direction at a constant speed, and then turning (no slowing down). I do this all the time in my tactical escort retrofit when I hit AP:A. Or in my b'rel retrofit when the enhanced battle cloak is on.
What you are describing is slowing down then turning. Of course you're going to slide, because you're still decelerating.
The slides you talk about mostly happened when the game first came out, the Sovy' was an extreme "drift-ship" (kinda like a drift-car). I used to use it to keep a bead on a ship while still moving in another direction, it was fun. Now, pretty much the only way you will see it is in sector space, because they never changed that portion of the game to reflect.