Trying to figure out difference between Effect > Path > Offset and compound path action

Hoping someone can help me figure out the differences between the manual Offset Path function and an action my client created that results in an extra compound path. I'm trying to get the compound path and offset functionality working in a script routine. The script routine (from this thread) is: 

var createOffsetPath = function(sel) {
    var offset = 9;
    var xmlstringOffsetPath = '<LiveEffect name="Adobe Offset Path"><Dict data="R mlim 2 R ofst value I jntp 0 "/></LiveEffect>'; // 0 = round, 1=bevel, 2=miter
    xmlstringOffsetPath = xmlstringOffsetPath.replace("value", offset);
    sel.applyEffect(xmlstringOffsetPath);
}

This is the original filled group with a single path: 

This is the image after I create the offset using Effect>> Path>>Offset Path. Note there is still just a single path in the group. 

This is the client's action step:
 

This is what I get after running an action step on the original group. Note there is now a path and a compound path: 

Does anyone know how the action got this compound path effect? I'm trying to mimic it through the scripting process I'm working on. Thanks in advance.