Material Instances do not stack in the Blendables Array for a Post Process Volume

Given two Material Instances of one material applied both to a Blendables Array only the second (last applied) will be applied to the post process volume.

With the same setup, two Materials will stack the effects of each blendable.

With Materials:
[Image Removed]

With Material Instances:
[Image Removed]

Also Reproduced in Main Promotable-CL-2487422

Assets and Level for Testing added in CL-2489498

Assets and Level for Testing added in CL-2489498

1. Open QAGame Editor
2. Open World'/Game/Developers/EricKetchum/Mat_Inst_PP/Mat_Inst_PP.Mat_Inst_PP'
3. Enable Post Process Volume in Level marked Using Materials
4. Disable Post Process Volume in Level marked Using Materials
5. Enable Post Process Volume in Level maked Using Material Instances

RESULTS: (See Attached Images) PPVs are rendering different results of blendables

EXPECTED: Both PPVs should render exactly the same.

Setting multiple material instances of the same type as blendables doesn't work