New Code for Resisting Lateral Loads, Mathewson, Journal of Light Construction, 2009. According to this article prescriptive ledger connection was also added.
2015 IRC - R507.2.4. It looks like 2015 is the first occurrence of the 4x750 lb option.
Note: 2018-2021 2021 IRC R507.9.2 is where this provision is "currently located" along with a whole lot more tables and requirements. It's still a 1,500 lb load. Be aware that they like to move these provisions around a LOT. So don't expect that code reference to "sit still" for very long.
