I think we need to review if a technique is really changing, or is something else is going on?
I posted on Kenpotalk earlier this week about the technique 'Scraping Hoof'. Working with Mr. Planas, I learned a different way of executing the technique from that which I originally learned. I do not think Mr. Planas is showing me the technique as a changed technique, I think I learned the technique differently from how it was originally designed. Mr. Planas, I believe is a stickler for 'Tradition'.
What is needed to make an accurate determination of any 'changes' is the 'Rosetta Stone'; what was it like, what changes were made, and what is it like now.
One example that is discussed regularly is the American Kenpo Technique 'Five Swords'. The 'original' technique had a right spear hand thrust to the diaphram, the 'altered' technique changed this to an uppercut punch. This change was put in place because most practitioners do not train their finger thrust to a weapon strength; the spear hand is an ineffective weapon.
I don't like the term 'evolve', especially, because we, as human practitioners, haven't grown any new limbs. Our natural weapons, and the methods of executing with those weapons really don't change, do they?