I agree with you but............... since it is law here to wear a helmet is it correct of the ins company to assume he wasn't, seems to me to be the opposite, unless the ins company have actual evidence to say he was not wearing a helmet then IMO they are on shaky ground, perhaps legal intervention is an option here.
also -
I don't trust hospitals here, they are money making scams and this poor guy is a cash cow, keep him in intensive care likely in an induced coma - and the money rolls in - he can't stay there for ever