Foliage is not partially loaded after InstancedFoliageGridSize is changed by WorldPartitionFoliageBuilder commandlet

Changing the InstancedFoliageGridSize by the WorldPartitionFoliageBuilder commandlet will cause some of the foliage to not load correctly.

[Reproduce]
1. Create a new project and create an OpenWorld map.

2. Paint near the origin using the foliage tool.

3. Close the Editor.

4. Execute the WorldPartitionFoliageBuilder commandlet and set "-NewGridSize=51200".

5. Open the Editor

6. Open the map from Step1, and PIE.

Then it appears that only about 1/4 of the foliage area is loaded.

[Reproduced project]
1. Download the project from the comments link.

2. Open the map "LV_Sample1_Source".

3. Run PIE. The foliage around the cube placed at the origin. (Sample1-Base(OK).png)

4. Exit PIE and open the map "LV_Sample1_Cnverted" converted with NewGridSize=51200.

5. At this time, The foliage around the cube placed at the origin is partially missing. (Sample1-Converted(NG).png)