Vertex Interpolate Node Doesn't Work with Lightmass

The vertex interpolate node doesn't work with lightmass.

Found in 4.19 CL# 4033788, 4.20 CL# 4233996, and 4.21 CL# 4258917

1. Open attached project
2. Look at the Red Sphere and Blue Sphere

Results:
The red material with the vertex interpolator node will not affect the color of the indirect light while the blue material will

Expected:
They should both respond the same