No, it's like you said - it's edge triggered, but it has to see the OFF and then ON. When they are used in a Stage, this makes it very difficult to edge trigger. One way to make this work is at the top of your program before ANY stage:
STR S1
OUT C0
So C0 would be OFF every scan S1 is NOT enabled. Then in the Stage logic for S1, use STRPD C0 (or actually just STR C0) which would cause all those instructions see the edge on the 2nd scan that S1 runs.