In short, you are discussing a knife versus knife duel - one of four generic knife fight confrontations...
1) Knife vs hand
2) knife vs stick (or any impact weapons)
3) Knife vs knife (or any edged weapons)
4) Knife vs gun threats
Of these super generic confrontations...you would have to worry about your wrists/inner arm muscles if you were fighting...
Unarmed vs the knife attacker.
Weaponed versus a knife attacker.
It is not crazy or unsound to try to keep your hands turned in, BUT! In the fight, when you strike, grab or grapple, or just reach out to do this...you MUST at some point expose those body parts! Its sort of like the whole fighting stance theory discussed here:
http://www.hockscqc.com/blogs/08-08/index.htm
...in a way. If you can make the same jump/connection conclusions between the discussion of the hip front or back with the hands turned in or out. So in a quick defense moves? Sure, turn limbs in. But you can't stay like this through a whole fight. When fully engaged in the scenario, a stance is usually gone, and it almost becomes almost impossible to maintain a statue-perfect, fighting stance with all body positions in perfect photo posture...limbs turned in...when battling the bad guy.
Hock
(And if someone takes a still picture of you in this take-action process, this still photo can be misconstrued by morons and simpletons who complain you are untrained and unfoolish because you were not protecting these body parts versus a knife.)