The Archer's Distillation description says:

Combines two vectors (a position and a direction) into the answer to the question: If I stood at the position and looked in the direction, what block would I be looking at?

And then:

the so-called "raycast mantra," is Mind's Reflection, Compass Purification, Mind's Reflection, Alidade Purification, Archer's Distillation. Together, they return the vector position of the block I am looking at.

my issue is with the words "If I stood at the position". If I stand at a given position, then my eyes are 1.6. blocks above my feet. If that is accurate, then the "raycast mantra" as described would:

• get my eye position
• stand at that position (thus adding an additional 1.6 blocks vertically)
• shoot a ray in a direction parallel to my view direction (but 1.6 blocks higher)

but that would not "return the vector position of the block I am looking at"

The raycast mantra description is accurate, the Archer's Distillation description could be more precisely "If my eyes/head was at the position and looked in the direction..."