I deal with insurance companies for a living and they have all invested heavily in anti-fraud systems over the last few years. Your friend should not even consider altering 'the facts' or he could very easily become one of the examples that the insurance companies are looking to expose in order to discourage further fraud.
All claims are throughly investigated, so he should correct any inaccuracies immediately, before the real facts speak for themselves and he finds himself having to explain why he lied to the authorities.