None of the cancelable normals jail if canceled into SK if the opponent is ducking, not even 23f2 which is +25 on block cancel. What I mean by not jailing is that they can let go of block before the SK and it will miss in any situation. SK will only jail on standing block, which means they can not let go of block, and punish before SK.
It seems that SK behaves like a true high when canceled.
Will NOT jail on standing block: 1SK, 23SK, b1SK and b3SK. The rest will jail ONLY on standing block.
They can punish every ducked SK, be it naked or canceled if they block low. So, if you start a blockstring on a duck-blocking opponent, and he is aware of this, you better finish it in staffgrab, low rang or OS.
But, the frame advantage on every cancel is different. Since SK is 37 frames duration (including execution), means you can count the disadvantage you're at. For example: 1 canceled on block is +13, which will make SK -24 if it is canceled on a ducking opponent and he lets go of block before the SK. Every character can not only uppercut you here, but even full combo punish.
The best are 34 and d4 which leave her at -11. b32 and 23f2 leave her at -12 - so once the opponent gets the hang of it he can punish you with a full combo since almost every char has a 12 frames and less combo starter.