I'm not sure this mailing list is a right place for reporting bugs(?) 
in pkgsrc documentation.

pkgsrc.txt:
8.13. Using 'sudo' with pkgsrc

       When installing packages as non-root user su(1) feature of
       pkgsrc, it can become annoying to type in the root password for
       each required package installed. To avoid this, the sudo
       package can be used, which does password caching over a limited
       time. To use it, install sudo (either as binary package or from
       security/sudo) and then put the following into your /etc
       /mk.conf:

    .if exists(${LOCALBASE}/bin/sudo)
    SU_CMD=        ${LOCALBASE}/bin/sudo /bin/sh -c
    .endif


First, this .if doesn't work.

Second, IMHO it is better to NOT use pkgsrc version of sudo
for building pkgsrc packages just because A wants B and B wants A...
It is much better (and IMHO it should be recomended in pkgsrc.txt) 
to use external (/usr/local?) sudo.
In this case it may be used for bulk builds
or by pkg_chk (latest version of which supports this).

P.S.
Why NetBSD base system doesn't contain widely used sudo and contains
lots of rarely used (and not mandatory) software?

P.P.S.
Is there mailing list where I can ask my "why" questions? :)

-- 
Best regards, Aleksey Cheusov.