Hierarchical Instanced Static Mesh components that contain no foliage are disappearing when ShowFlag.InstancedFoliage 0 is used.
This was reported and tested in 4.24.3 (CL-11590370) and reproduced in 4.25.3 (CL-13942748).
Results: The HISMC will be hidden
Expected: HISMC that isn't grass will stay visible
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-96106 in the post.