Head binding now and the past

[Anomalocaris]

head binding does  not directly tweak any DNA.    Using you orchestra analogy, head binding caused nothing that is the equivalent of of even a single orchestra member being lost, nor have the effect of causing any member to play differently then he/she had done before.

Stem cells can be manipulated either by mechanical and chemical means basic genetic science.
What affects drive genetic change relative to mechanical stem cell manipulation over generations is not a well researched topic only some old proof that regeneration through breeding has a degree of immunity to a damaged parent negatively impacting there offspring. We do know if we damage a worm bad enough it grows back the wrong half that's about as far as it goes.
I suggest they try being nice the worm and see what effects can be stimulated by mechanical means.

I think some conceptual confusion needs to be cleaned up.

1. The only stem cells in parent organisms that directly affect descendants organisms are the stems cells which develop into gametes.    tempering with any other stem cells in the parent organism may change how these cells develop in the parent organism itself, but not how any stem cell develop in descendant organisms.

2. the only way to temper with stem cells destined to become gametes that will go on to influence how stem cells in descendant organisms will develop into differentiated cells is to edit its DNA.    tempering with the development of stem cells in any way will not cause the effects of the manipulation to also manifest itself in the development of the stem cells in the descendant organisms.

So no, using chemical or physical means to manipulate how worm embryo develop so as to  cause the worm to grow two heads will not cause the worm’s descendants to become more likely to also grow two heads, provided two headed worm is able to reproduce in the first place.