Why can't turn off hyphenation by Script?

This works very will with version EN, not work with version JP

1. alert (app.activeDocument.textFrames[0].paragraphs[0].paragraphAttributes.hyphenation); 
2. if (app.activeDocument.textFrames[0].paragraphs[0].paragraphAttributes.hyphenation == true) { 
3.     app.activeDocument.textFrames[0].paragraphs[0].paragraphAttributes.hyphenation = false 
4.     } 
5. alert (app.activeDocument.textFrames[0].paragraphs[0].paragraphAttributes.hyphenation); 

If you try this code, it will not working in version EN:

1. alert (app.activeDocument.textFrames[0].paragraphs[0].paragraphAttributes.hyphenation); 
2. if (app.activeDocument.textFrames[0].paragraphs[0].paragraphAttributes.hyphenation == false) { 
3.     app.activeDocument.textFrames[0].paragraphs[0].paragraphAttributes.hyphenation = true
4.     } 
5. alert (app.activeDocument.textFrames[0].paragraphs[0].paragraphAttributes.hyphenation);

I think, the cause we can't set hyphenation or any attributes, if all attributes of Paragraph the same setting of Paragraph style.