My feeling is that TA cannot guarantee that the market will not be moved by random extraneous events and/or new "fundamental" data points, but those typically have an effect for a few days at most and then the market eventually responds to its TA biases. For example, if the market is OB and something happens, like an especially good earnings report, that drives it even more OB, it just increases the probability that the selling will begin sooner and will be more severe. Even under manipulation by outside forces like the Fed liquidity policy, TA still applies as an overlay to the manipulated bias. Intraday especially, there are still OB/OS trading opportunities.