A response to the question has just been offered on the ExpatForum site which may be more in line with the desired response sought.
I would offer this thought: the benefit is available up to a £50k cap, in a country where the average wage is roughly £28k. Would someone feel comfortable offering a reason for not including the amount as income on a 1040 as "it's a 'public assistance payment' for 'low income families'"?
Yes, the problem is CBT and yes, we've discussed 17(3) before. What is offered on ExpatForum is the likelihood of a return being challenged. That's territory best left up to the individual filer, and their tolerance for compliance versus risk.