In the latter case you assume Soun knows the technique, or would know someone that does, since ms Tendo died already at that point.
Plus, if you do that to a little girl (Akane was only a little girl when her mom died), there's bound to be a change when puberty hits. That's known to almost rewire the brain so to say, so any mental blocks that ever introduced as an alien influence from the brains point of view could potentially be broken down, rendering the technique useless, restoring any memories and whatnot (provided we assume the technique blocks memories, rather then remove them, since that's also the evidence given by the relevant episodes in canon).
Whil it may account for some of the abusive behavior she exhibits, I'd expect more changes then just that to take place as a result of the technique being countered by nature.