Not a materials scientist but argon-oxygen is a common first step in plasma cleaning surfaces (critical especially for allowing whatever you want to CVD to adhere properly to certain metals) before applying primer. (It's also used in nitride hardening aluminium.)

Considering how large GE is, I wouldn't be surprised if they had it 'on tap' in a PLT automation network and they take bulk delivery from a supplier every month or two. and some bad process engineer forgot to add a sensor check in loop (or his manager just told him to "screw it, argons cheap, no need to add a flow meter to this process" as a cost cutting factor).