Fair question. Im not the author so can only make a guess (other readers of HN surely know far more than I about these subjects). However I suspect the rationale is related to whats been called "Bernstein chaining".

https://cr.yp.to/proto/ucspi.txt

http://www.catb.org/~esr/writings/taoup/html/ch06s06.html

https://skarnet.org/software/execline/grammar.html

https://www.oilshell.org/blog/2017/01/13.html