The article say that "Next.js is well-specified." I... don't think this is actually true. It certainly has lots of documentation, but as has come up time and time again, there are tons of undocumented or poorly documented behaviors that have been the cause of consternation.
So I kinda wonder, did they just create the framework that Next.js claims to be but never has been? And is Next.js without the hidden stuff actually a good framework? Who knows.