Even if context became part of the argument, unbalanced powers are still unbalanced.
So let's say Sacred Guardian was amended to only work for Food Dogs. Except, when someone builds a custom power, that power is usually based off existing powers. That's the recommended approach. So what's to stop our friend A.Munchkin from taking a power exactly similar to Sacred Guardian, but only works for minitiarized giant space hamsters instead, or whatever bullshit concept he's trying to sneak past the table? Granted, the GM could just say no way, but in that case, there would be no point in restricting Sacred Gurdian anyway, since the GM wouldnt allow it even without that note.
Personally, I think Sacred Guardian should just be rewritten. Foo Dogs []ishould[/i] have a power like it, but it should cost a lot more.
As an aside, I'm not entirely sure it's out of context, exactly, to allow Sacred Guardian to apply to social and mental conflicts. If hat was intended, though, then yeah, it should cost a hell lot more.