The Iron Soul Monastic Tradition in Psionic Power includes Mental Arsenal:
Mental Arsenal: While wielding a weapon other than one in the unarmed weapon group, you gain a +1 shield bonus to AC.
Now, "shield bonus" is a mechanical term for a kind of bonus (so it doesn't stack with other bonuses of the same kind), and shield bonuses always apply to AC and Reflex defenses (PH1:213, RC:27:267, HotFK:327, every other shield bonus I've ever seen granted by an item or power or feat or feature).
Does Mental Arsenal grant +1 to Reflex because it grants a shield bonus, and shield bonuses do that? Or does "to AC" imply an exception to the rule (and if so, why not say what it doesn't do instead, and why make it a shield bonus in the first place)?