Confusing (possibly broken?) documentation of for-label requires

When documenting a module in a package, I get different behavior depending on whether I import the module with (for-label "mod.rkt") or with (for-label collect/mod). In particular, in the first case, many of the hyperlinks in the generated html are missing and underlined in red. It works as expected when using the second require. This is misleading because the examples in the documentation (how-to.scrbl) requires modules for-label as path strings.

Example in a package 'scrib_test':

File doc.scrbl

#lang scribble/manual

@(require (for-label racket
            "mod.rkt"))

@defmodule[scrib_test/mod]

@defproc[(some-fun [x any/c])
         string?]{fun}

File mod.rkt

#lang racket

(provide some-fun)

(define (some-fun x)
  "fun")

Start with the for-label examples in how-to.scrbl and reproduce the scrib_test case using doc.scrbl and mod.rkt. Compare generated HTML for the path-string and collection requires, then trace the documentation behavior involved. Done means both forms produce the expected hyperlinks without red underlining.