the steering arms are part of the lower balljoint, so putting spacers between them and the spindle effectively shortens the tierod length, thus toe out occurs. [i'm talking rear steer, factory setup] in other words, the steering arm must physically be pushed inward to bolt up to your tierod assembly when you didn't alter your tierod length after you used the spacers. the tierod needs to be lengthened to get the toe back where it should be.
Maybe you need to go look at that again.
You are changing the relationship of the steering arm to the spindle, not to the LCA, or the tierods. the tierods relationship to the steering arm is fixed by the location of the LCA ball joint mounting hole. Unless you are only putting one spacer ont he spindle then it matters not.
Odds are better that all the front suspension work he did is the culprit, I quote
I just got my tires back on the ground after a suspension overhaul. New QA1 UCAs, QA1 LCAs, Hotchkis/Fox Shocks, 1.14" Torsion bars/Hotchkis lowering leaf springs, fresh lower ball joints...and Mancini's camber spacers.
