REGRESSION: ATTR_light_level directive in custom attributes is reset in newer exporter

[GlidingKiwi]

When trying to use the latest exporter (4.20RC1), I get a strange result for all objects with an ATTR_light_level attribute:

The export result is correct using the 4.0.0 exporter (using Blender 2.93)

I will send a simple Blender file to Ben via Slack that allows reproducing this issue.

[bsupnik]

Hi,

I want to make sure this is a correct summary of the bug:

• The test file has an ATTR_light_level that is meant to cover a WIDE variety of elements attached as a CUSTOM property of a mesh that is a parent to a bunch of other stuff in the hierarchy.
• No light levels are set on the materials or meshes anywhere within the hierarchy.
• The expectation is the light level will apply to the entire set of meshes.
• The actual result is that the light levels are reset before each mesh and have no effect.
  Could you please post the CORRECT OBJ from 4.0 as you expected it (OBJ output) to this ticket?

[GlidingKiwi]

As requested, here is the output from the 4.0.0 exporter of the test file:
Signs_test.zip