Great topic, and happy to learn that about Chad ! The Reverse Dry Shake was probably influenced by the pastry word (pastry chefs being customers, or in the same team with bartenders in a restaurant or a hotel). As when they whip egg white to make meringue, they always chill the egg white first, so it’s more efficient.
By the way, what is so strange in the bar industry, is to see bartenders arguing about using Dry Shake or Reverse Dry Shake method and talking usually about the visual result they get, and not the taste (this wouldn’t happen in with cook chefs…).
I mean what is really interesting about the Reverse Dry Shake, is you can use 1/4 (10 ml) of the egg white quantity used with a Dry Shake (40 ml - equivalent to one egg white) to get as much foam (the bubble will be more compact and the foam more white with 40 ml than 10 ml).
So it means you will have a more flavorful drink with the Reverse Dry Shake, as it would be like adding 10 ml of water, vs, 40 ml of water into your drink. And if you just want a nice foam on the drink, 5 ml of egg white are enough.
Don’t forget fresh egg white have more proteins than pasteurised egg white, so they are more efficient.
The use of eggs in the 19th century drinks was probably a way to feed the customers if the saloon. So when it’s rich/dens, you are not hungry even.