Separate objects don't deform together when rigged

Support Animation and Rigging
1

I’m new to the rigging part of Blender, though I’ve done modeling for awhile and used Lightwave extensively before. I’ve created and rigged a character (think Funko Pop type character) where the head and eyes are separate objects. When I rig the character and ensure the weight paints are completely 1 (red) for both the head and eyes, I still get deformations when I rotate the head. I was expected the head and eyes to move together, as if the eyes were parented to the head and I was just rotating the head.

Is my expectation wrong or am I doing something wrong in the rigging process?
Here’s a quick picture to show the issue:

Character
Character960×540 174 KB

2

Weights are relative to other bones. 1.0 doesn’t necessarily mean fully weighted. Select a vertex in edit or weight paint and look on sidebar/item/vertex groups. If your vertices are weighted to any other bones, they’re not fully weighted to head/eye.