If you look at thousands of overbought and oversold signals and compare the ones which failed to the ones that work, you may find that "overbought" and "oversold" is a concept that overall does not work for Forex (especially during trending markets), i. e. does not really give you an edge.
(And if you turn "overbought" and "oversold" upside down - i. e. TR in the direction of the extreme hit - it still is the same concept,)
Lots of people use it, lots of people claim it works - I just haven't seen any trustworthy statistic (with a big enough corpus) that supports the thesis...