Metallic Setting is not passed through Material Function in Feature Level ES2

When a metallic input is passed into a material via a material function and previewed in ES2, the metallic is always returns 0 in the material.

Also reproduced in Main Promotable-CL-2490775

[Image Removed]

1. Unzip attached AH_Metallic_ES2 4.8.zip
2. Open AH_Metallic_ES2.uproject
3. Play in Mobile Preview

RESULTS: See Attached Image, Sphere assigned a Metallic Value of 1 through a Material Function is returning 0.

EXPECTED: Spheres should be identical.