1) Take brace off while waiting for registration.I would tell your friend to think long and hard about it, the amnesty period does not say they will be approved, if the form is submitted and it takes more than 88 days to get the approval back, it is an automatic denial and the ATF has said they will then take enforcement action, and since your friend now has been denied an application for a SBR that he told them where it was, and who owned it...It makes for a pretty easy enforcement action.
Have your friend ask himself, why this particular form for this program requires a photograph, when that is not normal practice...those are things I would be telling my friend and would make me think....hmmm....
I would tell your friend to find a 16 inch upper and stick it on the rifle and see how this plays out. Or sell the firearm before it is published in the register.
2) Photos are required so folks without braces do not try to get free registration