He's also behind expand-region! (Although, I've started experimenting with the much-smaller treesitter-based https://github.com/casouri/lunarymacs/blob/master/site-lisp/...)

I'm pretty sure when he wrote all of that stuff that he'd only been using Emacs for around a year. The benefit of someone that talented, or groks Emacs immediately, and is familiar enough with the outside-ecosystem to know what he wants to borrow, I suppose.