I know that in the past, when I've had to re-get all of NetBSD in stages,
I've been able to use sup -o to get only the files which differed each
time, age notwithstanding.  For example, interrupted sup -a invocations
could be resumed where they left off with -o.  I find that -- contrary
to my own rather loud advice of last night -- with the current
sup.netbsd.org, this isn't working; my current sup is regetting everything.

What's up?  Why the difference?