My name is Yamaguchi and electronics engineer in Japan.
FB3 should be connected to VOUT3 for fixed output voltage version.
I'm confirming with the designer. Let me get back to you in a day or so through here & local FAE.
Thank you for the answer.
Thanks a lot,
FB3 should be tied to the output for fixed voltage version. I am the applications engineer for this product and the answer is confirmed by the designer. The datasheet will be updated accordingly.