Don’t pretty much all OSes implement process startup in userspace? On macOS, the kernel creates a process with an image of dyld and points it at dyld_start, which actually takes care of parsing the Mach-O header. I assumed ld.so does the same job on Linux.

It is almost as if you agree with the authors ..

"In this paper, we argue that fork was a clever hack for machines and programs of the 1970s that has long outlived its usefulness and is now a liability"

(But thanks for the good explanation)