The Gumball does not seem to center normally while selecting a spotlight. With the Gumball in Orient to CPlane mode, I would expect the gumball to appear in the volumetric center of the spotlight’s bounding box. This only works when selecting in Top (or Perspective). If you select in Front or Right, then the gumball centers in a different place. The further the spotlight is from the origin, the larger these differences become.
Rhino8 SR3 (8.3.24009.15001)