It's in the files as a physics tech, but it does seem to be a bit of an odd one as all the other resource techs are under engineering and the mining tech is in engineering as well. At some point in development they probably had the strategic resources split up, but put them all back in engineering for release and forgot to change the tag.
If you want to do it yourself, it's in stellaris_install_location\common\technology\00_strategic_resources_tech.txt, just change the "area = physics" line to "area = engineering", both at the top and under the weight modifiers.