distdir unset in subdir Makefiles?

[David Fang]

Hi,
        I've noticed that the distdir variable in generated Makefile.in's
only appears in the top-level Makefile.in, however, it is not set in
subdirectories' Makefile.in's.  Is this intentional? According to the top
Makefile.in, distdir and top_distdir are passed down recursively during a
"make distdir", set to $(PACKAGE)-$(VERSION) and subdirs.
        In one instance, I wished to manually inspect the result of one of
the subdirectories' "make distdir", but had to pass in these two variables
by hand, slightly inconvenient.  Is there a rationale for omitting these
two variables in subdir's Makefile.in's?
        Thanks in advance.

Fang