The documentation is complete. The problem isn't a problem. That the documentation refers to other documentation may be annoying, but it is complete. And, whether you like it or not, every single person who worked/works on the Perl sourcecode and nearly everyone who worked/works on the Perl design is fluent in C and has no problem with statements like that. In other words, any single person who would have ever worked on the documentation is fluent in C and has no problem with statements like that.
There are several incorrect statements there, but I'd just like to say that I at least have a problem with such statements in the documentation. They don't belong, and should be fixed; it's just a very low priority to me.