I still refer to the same book for a lot of stuff but some things have moved on like you say. The only thing I’d recommend argon /2% O2 for is MAG welding carbon steel sheet metalwork where the cosmetic appearance is more important than the structural integrityI took reference from 'the science and practice of welding; 1981' it makes mention that for (I was in error) dip transfer welding Argon+2% oxygen is used, 'provided the additional oxygen can be tolerated'
The addition of oxygen raises the arc temperature, increases fluidity and wetting out of the weld pool:
Bear in mind, that I've had this book since 1981, things change, improvements are made all the time