I think the positions you are asking about is sela (See-Laws) position. The silat player can go into the sempak or dempak position (a standing twist leg position that either your lead foot steps behind, or your rear foot step forward into a twist stance). For example:
Attacker does a front kick:
I would take my lead foot behind my rear leg (Treat Step) while do a blocking or destruction to their shin. Once their kick is no longer a threat I would then step forwards with a kick and/or other counter.
Attacker does a wheel kick:
Drop straight down into the cross leg sitting position to duck the kick. Now let say the attacker see that you are now sitting and then tried to kick you in the head. Scoop his front kick with your right arm as you stand back up. Kick to his groin, or susporting leg.
The sempaks and dempaks can be use to Evade attacks or you can attack from these position as well. The sitting position can be used to bait your attacker into attacking you because your sitting down and appear to be at a disadvantage position. This is only a few of the uses of these techniques. Hope this helped you understand better.
