I'm surprised that Cook's magazine didn't properly identify this method, it is at least 3/4 of a century old. It is called "High-Ratio Cake" method or, alternately, "two-stage" mixing. "High-Ratio" refers to the ratio, by weight, of sugar to flour in a cake mix. When the weight of sugar is higher than the weight of the flour, the creaming method doesn't work as well as it should because the amount of sugar in the mix is too high to form a stable emulsion with the fats in the mix and there isn't sufficient structure from the gluten in the flour and the proteins in the eggs to hold the whole thing together well.
A short history to explain:
All of the "butter cakes" that we make here in the West are grand-kids of the English Pound Cake ( 1 pound butter, 1 pound sugar, 1 pound eggs, 1 pound flour). In the days before electric mixers, the easiest way to produce these batters by hand was the creaming method: cream soft butter with sugar until light and fluffy, cream in eggs one at a time and then stir in flour. When planetary and spiral mechanical mixers became standard in the industry, somebody figured out that this practice could be shortened into two stages by mixing all the dry ingredients with the fats for the first stage and then slacking the mix with the liquid ingredients for the second stage which called for beating the completed batter for a measured period of time to activate the gluten in the wheat flour just enough to hold the cake together without making it dense or tough. It can be a little more complicated than that but I did just exactly what I wrote above for more than 11 years for a German's Chocolate Cake formula I used at a restaurant in New Haven. I did it this way mostly because I could let the mixer go without supervision while I did two or three other things.
For anyone who is interested there's a wonderful book that was written by the great baker Rose Levy Berenbaum called <span style="text-decoration: underline;">The Cake Bible</span>, where all of the cakes are made this way. Rose was one of the early proponents of this professional method and she introduced it to home bakers in a series of articles in various cooking magazines in the Eighties.
Tomturbomatic hit the nail on the head: High-ratio method was the beginning of the packaged cake mix when it was expanded from pancake mixes.
