NODATA value is not masked after adding NODATA option of titiler

[JinIgarashi]

In RasterTransform feature, I added nodata=-9999 to titiler endpoints, but this value is not becoming transparent (masked).

The below URL is titiler's /statistics/ endpoint.

https://titiler-dev.undpgeohub.org/cog/statistics?url=https%3A%2F%2Fundpgeohub.blob.core.windows.net%2Fuserdata%2Fa85516c81c0b78d3e89d3f00099b8b15%2Fdatasets%2FDem_Rwanda_10m_allt_20230921150153.tif%2FDem_Rwanda_10m_allt_20230921150153_band1.tif%3Fc3Y9MjAyMy0xMS0wMyZzcz1iJnNydD1vJnNlPTIwMjUtMDQtMjJUMDclM0E0OCUzQTIzWiZzcD1yJnNpZz1SMFYyb1VSZW5WZ0U4JTJGb2tSMnElMkZWSnVOVG9lWmpEVW9FM2VlcTclMkJ5WTNjJTNE&histogram_bins=10&expression=where%28b1+%3C+2112%2C+b1%2C+-9999%29%3B&nodata=-9999

statistics endpoint response

{
   "where(b1 < 2112, b1, -9999)":{
      "min":-9999,
      "max":2111,
      "mean":-89.04128130744485,
      "count":974848,
      "sum":-86801715,
      "std":3201.58412936971,
      "median":1287,
      "majority":0,
      "minority":100,
      "unique":1226,
      "histogram":[
         [
            87301,
            0,
            0,
            0,
            0,
            0,
            0,
            0,
            392128,
            495419
         ],
         [
            -9999,
            -8788,
            -7577,
            -6366,
            -5155,
            -3944,
            -2733,
            -1522,
            -311,
            900,
            2111
         ]
      ],
      "valid_percent":100,
      "masked_pixels":0,
      "valid_pixels":974848,
      "percentile_2":-9999,
      "percentile_98":2039
   }
}

As you can see, -9999 is set to min, and 0 pixel is masked from statistics api. Titiler doc says NODATA option will overwrite internal no data value, but the behaviour looks very weird (see the below screenshot from geohub).