python - Different results from GDAL raster attribute table command on mac and windows

I am trying to get the raster attribute table of the following file: Shift_cult_past_current_prediction_20160107_gr1DD.tif available here: https://www.dropbox.com/s/fmomfpro3j6dmz8/Shift_cult_past_current_prediction_20160107_gr1DD.tif?dl=0

Here is the code I am using:

import gdal
dataset = gdal.Open(dataset_uri) # dataset_uri is path to .tif file
band = dataset.GetRasterBand(1)
rat = band.GetDefaultRAT()

I am using gdal version 2.1.0 on python 2.7.11 (Mac and windows). However, while I get the raster attribute table on windows I get nothing on mac (10.9.5). What could I be doing wrong?

-- EDIT

$ conda list | grep 'gdal'
gdal                      2.1.0               np111py27_1    conda-forge