This doens't have to do with your point, but it reminded me,   I've often wondered about that verse. (Mark 7). I have two possible thoughts--One, maybe Jesus was testing the woman to see how she'd answer that. OR, maybe Jesus too was growing and learning, thinking first that his mission was limited to the Jews, but thru encounters like this one, he deepened his won understanding, eventually realizing that his mission was to all. 
What do you think?