Futaba Sbus does not work for FS

I have an T32MZ Futaba Tx which has a very nice layout for defining your FailSafe desires. I am using a variety of Futaba Rx, but the R7108SB is one of them. It has been set in Mode B using the button at the top of the Rx. When the Tx is turned off, all the servo attached to the Ch 1-7 outputs does what they are programmed to do. However the outputs attached to the Sbus hold their positions regardless of the FailSafe setting prescribed by the Tx. Is this a flaw in the Futaba arrangement or is it purposely done for some reason? Is there another way to get the Sbus outputs to respect the FailSafe setting defined in the Tx? Many thanks to anyone able to shed light on this dilemma! The reason this is being posted on the Ardupilot site is that my Sbus input is being sent to a Cube, and in manual mode I would like the RC side of things to dictate the response.