This problem seems to occur because Rotation is not taken into account when calculating Weight.
I have confirmed that it can be solved by calculating the rotation as follows.

float ULandscapeComponent::GetLayerWeightAtLocation(const FVector& InLocation, ULandscapeLayerInfoObject* LayerInfo, TArray<uint8>* LayerCache)
... 1991
// Find location
// TODO: Root landscape isn't always loaded, would Proxy suffice?
if (ALandscape* Landscape = GetLandscapeActor())
    const FVector DrawScale = Landscape->GetRootComponent()->GetRelativeScale3D();
    const FRotator DrawRotator = Landscape->GetRootComponent()->GetRelativeRotation(); //add
    FVector TestPosition = ((DrawRotator.UnrotateVector(InLocation - Landscape->GetActorLocation())) / DrawScale); //add

    float TestX = TestPosition.X - (float)GetSectionBase().X; //add
    float TestY = TestPosition.Y - (float)GetSectionBase().Y; //add

    // Abort if the test location is not on this component
    if (TestX < 0 || TestY < 0 || TestX > ComponentSizeQuads || TestY > ComponentSizeQuads)
        return 0.0f;
Steps to Reproduce

1. Open Landscape.umap in Content Example
[Link Removed]

2. Set Soil to Landscape Layers of Foliage
[Link Removed]

3. At this time, we should be able to generate Foliage only for the Soil part, but if the rotation value is set to Landscape, it will be an incorrect generation position.

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ComponentUE - LD & Modeling - Terrain - Landscape
Affects Versions4.234.24
Target Fix4.26
Fix Commit12372649
Main Commit12372649
CreatedFeb 19, 2020
ResolvedMar 23, 2020
UpdatedJun 22, 2020