<<Ronin...do you have an answer to the original question?
The answer is "no"... I cannot say why he does anything, as don't know the ~gentleman~! Now if he'd asked why ~I~ (or you) used this dynamic tenshin, well that would be a different question
If that had been asked, perhaps the vein-popping which some demonstrate (calling it dynamic tension) might perhaps be circus, silly melodrama? Or perhaps it is not the tightening which is the better benefit, but rather the letting go, the UN-contracting which is of fundamental value to the practice? Consider its pathetically easy to be tight, too easy, but how many can be supple without some extraordinary efforts I wonder?!?!?
Dynamic tenshin meaning contraction and uncontracting will generate the adrenal response and trigger the lovely horemones which I propose obviously need to be explored specifically in order to not be overwhelmed by them in intense serious/sudden situations. Not magic, not rocket science I would think, but I am puzzled by those who go over the top doing so and wonder the value of their eye bulging, vein-popping corinary on a stick expression... Is there ~fundamental value~ in what seems excessive demonstration?
Can ~dynamic~ be too much?