I would check the camera’s cull distance and foliage details and LOD settings for distance related stuff, also I think there is a distance scalar setting in the game overrides of the MRQ that is used to extend the cull distance or something like that. Not sure because never used it.
Edit: having watched the video again I think it should be something related to LOD levels, maybe you can force foliage to use LOD 0 and see if it works as expected.