It seems to me that the way the Settlement visa application is worded even if it was the UK Citizen that claimed the Child benefit, then that would still class as a breach of the immigration rules.

Section 8 of the SET(M) application form states:

“You must provide evidence that your partner is able to adequately maintain you and any dependants in the United Kingdom without recourse to public funds”.

The SET(M) form is dated 04/2013 so perhaps the rules have changed recently? Most of the advice on this thread is 2+ years old, which is why I was wondering if anyone has successfully applied recently and stated they were claiming benefits.