Objects are being selected when they shouldn't compared to doing it manually

Manually: I have one object(Main Piece). I duplicate it onto another layer (UG_OG). I use the "off_neg_1_16in" action I have. It selects the offset piece(Offset Piece) and nothing else. I change the spot color tent to 100%. End result is perfect.

Script: Does everything but after the action it still has everything selected and changes the color for all of them. End result is inncorrect. I should note it only does the offset on the UG_OG piece which is what I want. So im even more confused as to how the other 2 pieces are still selected

So even though after it does the action it should technically only have 1 object selected but has all 3 pieces selected. Are you suppose to deselect objects in the script every single time? I thought it would do this automatically if true?

I put safe guards in place to only change what I want but I was wondering if im doing something wrong? Why and How is a script completely different than doing it manually? 

Script doesn't show safe guards btw.

var ogPieces = [];
  for (var i = 0; i < paKOpieces.length; i++) {
    var og = paKOpieces[i].duplicate(REDLayer, ElementPlacement.PLACEATBEGINNING);
    og.name = "_UG_OG_" + i;
    setFill(og, "RED", 50);
    ogPieces.push(og);
    info("Created OG piece " + i);
  }

  app.selection = null;
  for (var j = 0; j < ogPieces.length; j++) {
    ogPieces[j].selected = true;
  }

  info("Running offset");
  runAction(ACT.off_neg_1_16in);

  if (app.selection && app.selection.length > 0) {
    for (var o = 0; o < app.selection.length; o++) {
      var item = app.selection[o];
      setFill(item, "RED", 100);
    }
  }