Epson L655 Duplex Setting

I underwent problem (well not problem apparently) when use printer Epson L-655 with USB connection. The printer has duplex function, to print on both side of paper without manual intervention. I use mac machine with O/S X 10 and run smoothly when i use duplex function with Wifi connection. See below chart 1 dialog window when we use wifi connection.

Chart 1 : Dialog Window with Wifi Connection

As you can see on chart 1 the dialog provides "Two-Sided: Off/On" dropdown list. However you will see the option on disabled condition when you use USB connection like chart 2 below.

Chart 2 : "Two-Sided" is disable with USB connection

What is wrong? The customer service answered to my problem without proper explanation and asking me to install remote access app in order EPSON technician able to review my system. While I was waiting customer office open on next day, I was trying to trouble shoot once again, and guess what: I found the bug, no, not really. Epson put the option "two-sided" with USB connection on different place, see chart 3.

Chart 3 : Two-sided Printing Settings in front of YOU

While on WIFI setting you need to select "Layout" first then select two-sided option printing, but with USB connection: it already in front of you.