According to my interpretation, here the main verb in the perfect indicates an act completed in the present time (the so called perfect proper vs. the aoristic perfect, which indicates a mere act in the past): we are now in the condition of being informed. The information regards the participation of Publius to a battle, a mere act in the past. Hence the sequence perfect indicative and perfect infinitive. It seems to me that D’Ooge is encouraging my interpretation through presenting first sentence 3.