gdal2Tiles output differs from MapTiler

I’m in need to process a large batch of Landsat images with MapTiler and since the version I’m using (1.0 Beta 2) does not support multiple input files, I created a simple python script that calls gdal2tiles for every file.

The problem is that using, apparently, the same settings, I get different coordinates.

This is the correct output from MapTiler:

 <?xml version="1.0" encoding="utf-8"?>
    <TileMap version="1.0.0" tilemapservice="http://tms.osgeo.org/1.0.0">
      <Title>mar_apr.tif</Title>
      <Abstract></Abstract>
      <SRS>EPSG:900913</SRS>
      <BoundingBox minx="-26.36147186954573" miny="-65.83667775218426" maxx="-21.96598523780907" maxy="-62.31334995428857"/>
      <Origin x="-26.36147186954573" y="-65.83667775218426"/>
      <TileFormat width="256" height="256" mime-type="image/png" extension="png"/>
      <TileSets profile="mercator">
        <TileSet href="6" units-per-pixel="2445.98490468750010" order="6"/>
        <TileSet href="7" units-per-pixel="1222.99245234375010" order="7"/>
        <TileSet href="8" units-per-pixel="611.49622617187504" order="8"/>
        <TileSet href="9" units-per-pixel="305.74811308593752" order="9"/>
        <TileSet href="10" units-per-pixel="152.87405654296876" order="10"/>
        <TileSet href="11" units-per-pixel="76.43702827148438" order="11"/>
        <TileSet href="12" units-per-pixel="38.21851413574219" order="12"/>
        <TileSet href="13" units-per-pixel="19.10925706787110" order="13"/>
      </TileSets>
    </TileMap>

And this is the incorrect output from gdal2Tiles:

<?xml version="1.0" encoding="utf-8"?>
    <TileMap version="1.0.0" tilemapservice="http://tms.osgeo.org/1.0.0">
      <Title>mar_apr_CLIP1.tif</Title>
      <Abstract></Abstract>
      <SRS>EPSG:900913</SRS>
      <BoundingBox minx="-25.32504747468283" miny="1.94797423573108" maxx="-21.33272919903126" maxy="5.10698976386579"/>
      <Origin x="-25.32504747468283" y="1.94797423573108"/>
      <TileFormat width="256" height="256" mime-type="image/png" extension="png"/>
      <TileSets profile="mercator">
        <TileSet href="6" units-per-pixel="2445.98490468750010" order="6"/>
        <TileSet href="7" units-per-pixel="1222.99245234375010" order="7"/>
        <TileSet href="8" units-per-pixel="611.49622617187504" order="8"/>
        <TileSet href="9" units-per-pixel="305.74811308593752" order="9"/>
        <TileSet href="10" units-per-pixel="152.87405654296876" order="10"/>
        <TileSet href="11" units-per-pixel="76.43702827148438" order="11"/>
        <TileSet href="12" units-per-pixel="38.21851413574219" order="12"/>
        <TileSet href="13" units-per-pixel="19.10925706787110" order="13"/>
      </TileSets>
    </TileMap>

Does MapTiler perform any other operations besides running gdal2Tiles?

Thanks in advance!