Let's assume that we all agree that /scratch is material of a transient
   nature.  The real problem is that the NetBSD core team imposed an
   undocumented policy that overrides whatever policy might have been
   in place.

No other policy could ever have been in place.  That code has been
present since the very first revision of /etc/daily in our source tree
(which means that it was inherited from 386BSD and 4.4BSD).

While I might agree that /scratch shouldn't be cleaned, that's no
excuse for tossing out nearly random accusations.