What is "the diode trick" in the diode compression discrete op amp?

[Boner]

https://www.diystompboxes.com/analogalchemy/sch/diodeopamp.html

Hoping this would get more insight then if I posted in the diode compression.


So what is the "trick" and what inspired the need for it?


I'm tying to figure out the circuit and to me it looks like a pair of phase splitters going into an amp. The inverted out going into the 100k resister and the noninverted out going into the diode, the two are added together into the final BJT that amplifies the whole thing, which makes sense to me when you think about what an op amp does. That's about as much as I can gleam from it.


So yeah what is the "trick" and what inspired the need for it?