Topic on Talk:Halo: The Master Chief Collection
Upon reviewing a few posts on the topic it does seem that a few variables in the UE4 ini files do interoperate with the settings in Blam. LowSpecGamer has also made a video showcasing this as well.
Looks like Reach in particular uses "[5]" for its array index on the setting values, I'm assuming the index is listed in OG release order with "[0]" being the universal setting for all games.
There is a risk of a lot of placebos slipping through the cracks, so the best thing would be to ensure that config fixes and tweaks are referenced to ensure validity.