No, it seems that I’m this case, the angular momentum of the light beam itself changes over time, a process that is typically referred to as (or driven by?) tor

No, it seems that I’m this case, the angular momentum of the light beam itself changes over time, a process that is typically referred to as (or driven by?) torque in classical mechanics, and so they used that term here as well. They call it “self-torque” (I believe) because it’s the light changing it’s own angular momentum. But I’ve not been involved with physics academia in several years, so take it with a grain of salt.