I just hit the site on my desktop. Like the steam controller before, it's got a lot of back buttons that you can likely remap (R1 to R4 and L1 to L4). So yes, the front buttons are backups.
Judging by the image in the "Speeds and feeds" section, there are only four shoulder buttons. Also, looking more closely at the placement, it looks like they're putting more emphasis on touchpads over the joysticks, and certainly over the D-pad, much like the Steam Controller.
