TWS 018 Captain America and Bucky have the following power.

"INSPIRING PRESENCE: Captain America and Bucky can use Leadership. Friendly characters within 8 squares that share a keyword with Captain America and Bucky can use Willpower."

I see nothing that prevents them from using willpower themselves. They are friendly (check) within 8 (check) and share a keyword with themselves (check).

So is there something I am missing, or does that power constructively give them willpower too.

I don't see any reason why they would not give themselves willpower. As you say they are within 8 squares and are friendly to themselves.

That's how I read as well.

yes, they give themselves willpower