Applying downscale causes textures to display unexpectedly on widgets

void FSlateUTextureResource::UpdateTexture(UTexture* InTexture)
{
	//...

		FTexture* TextureResource = TextureObject->GetResource();

		Proxy->Resource = this;
		// If the RHI data has changed, it's possible the underlying size of the texture has changed,
		// if that's true we need to update the actual size recorded on the proxy as well, otherwise 
		// the texture will continue to render using the wrong size.

#if 0
		if (TextureResource)
		{
			Proxy->ActualSize = FIntPoint(TextureResource->GetSizeX(), TextureResource->GetSizeY());
		}
		else
		{
			Proxy->ActualSize = FIntPoint(0, 0);
		}
#else
		if (TextureResource)
		{
			if (TextureObject->IsA<UTexture2D>())
			{
				UTexture2D* AsTexture2D = Cast<UTexture2D>(TextureObject);
				Proxy->ActualSize = FIntPoint(AsTexture2D->GetImportedSize().X, AsTexture2D->GetImportedSize().Y);
			}
			else
			{
				Proxy->ActualSize = FIntPoint(TextureResource->GetSizeX(), TextureResource->GetSizeY());
			}
		}
		else
		{
			Proxy->ActualSize = FIntPoint(0, 0);
		}
#endif