You can examine a dng file with exiftool utility and check is As shot WB tag present. It's not in the form of color temperature, but is given as 3 numbers (R, G, B channel multiplyer)
From my remembering, if WB tag is not present, then As Shot option in ACR gives the same result as Auto. So I think it is possible that WB tag is actually there, but color matrix is considerably wrong, so ACR calculates wrong color temperature from WB tag, but it won't go below 2000 K because it's the lowest settable temperature