If the character were the same age as the actor, you might exspect "about our age." However if Mendez were significantly older, let's say Mendez was in his mid-sixties, then referring to two younger men who were themselves 15 years apart as being about the same age might make more sense. Both are the professional uniformed armed forces of their civilizations. The Navy and Starfleet have many organizational similarities, and the rank structure for commissioned officers is the same. Defense first (break things and hurt people), everything else they're called on to do second. 15th century naval vessels and 21th century naval vessel had a few differences in equipment too.