What are we seeing? Describe your technique?

Al

He's air layering, putting a band of soil (or in this case it looks like sphagnum moss) around an upper section of the plant to encourage root growth while it is still attached to the plant.

And yes, the white nodes are what I would expect to see, they should be the starts of new roots.

I understand what layering is - I use it all the time to build top notch nebari on young potensai. I asked the OP to describe his technique - I'm not convinced what we're seeing are root primordia.

A layered tree:
{{gwi:6336}}

another
{{gwi:10873}}

a hornbeam prepared for layering
{{gwi:10879}}

Al