These two functions are marked interactive-only, yet the docstrings' last sentence starts "Interactively," which may lead readers to infer that they can be used non-interactively:
Interactively, N is the prefix arg, and
KILLFLAG is set if N was explicitly specified.
How about the following re-wording for the last sentence:
"A prefix arg becomes N, and sets KILLFLAG."
In fact, this solves another confusion: is pressing C-u "explicitly" setting N? It might seem not, but it certainly causes KILLFLAG to be set.