SplineIK requires -90 degree rotation when duplicating motion from it's own skeleton

SplineIK requires -90 degree rotation when duplicating motion from it's own skeleton

1. Download the attached project
2. PIE
   1. Result: Arrows follow each other
3. Open Arrows_AnBP and check the AnimGraph
4. Bypass the "CombineRotators" node, compile
5. PIE

Result: Arrows are not aligned (and spin out of control)
Expected: Arrows are aligned like after step 2