Within the ITF patterns many if the basic 'blocks' come from a crossed hand position.
In my own interpretation of this I use the crossed hands as the initial defence/block with the next movement as the beginning of the counter.
However, when watching karate kata or even old tkd patterns the position is not as common.
As seen here for won hyo starting at 2:44 https://youtu.be/OocodMeRKPQ?t=2m44s
Is it possible that the cross hands position became over stylised over the years?
Does anyone know where the positions came from?