Comment 3 for bug 1532586

See this bit of the documentation:

Note that @code{cl:require} and @code{require-system} are appropriate to load code
that is not being modified during the current programming session.
This notably includes the implementation-provided extension modules that @code{cl:require} can load.

I suppose it might have been intended to say "require-system behaves analogously to require" but it reads to me as if we are saying that REQUIRE-SYSTEM will load "...the implementation-provided extension modules that @code{cl:require} can load."

Reading your response, I suspect that this was not the intent.