What is accomplished by adding the egg yolk and white at different times?

I found via an earlier Genius Recipe (The Kitchn's Lofty Buttermilk Pancakes) that even just by stirring in the whites at the end, you get fluffier cakes. I mentioned this very briefly in the footnotes of this week's Genius article, but here's more on why that works: https://food52.com/blog/15690-a-genius-trick-for-fluffier-buttermilk-pancakes-no-whipping-egg-whites