We were told in Chapter 21 that Seacha had stripped Ares of the skill already. Unless the author is doing some real stupid hiding of information here, it makes the most sense to believe that Seacha used her plunder to get rid of it, and that her "it doesn't work like that" statement was about something else (like her aversion to using it due to her past), and not that it was physically not possible.
I assume that this means the hero aptitude isn't a unique skill, but it still feels really dumb to have Hero-ness stealable, and other skills not.