This was a request of the Blender Studio.
The Attribute color mode is used for more correct display of
materials during animation. The assets are created with
a color attribute that mimics the material.
The issue is that this attribute needs to be set up for every
individual object for it to work in Attribute color mode as
the lack of attribute will default the object to Object color mode.
This patch changes the defaulting to Material color mode
just like when using the Texture color mode.
Pull Request: https://projects.blender.org/blender/blender/pulls/143931
c0a0962450