I am the friend that’s building the wing.
Campgems :

You are correct about the dihedral is set on the previous step with epoxy and 6 hard wood joiners it’s not going to change. The washout jigs are angled as to put a twist on the wing they don’t set or change the dihedral. If the root is pined to the table why should it make any difference if the wing is 1”. 3” or 5” from the table the washout angel will not change.