> So I don't believe we use these numbers for anything.

Once you have a booted system, it doesn't matter; you have a real
disklabel and you're done.  But if you're the install procedure, you
definitely do use those numbers: they show up as the disklabel
geometry when you run fdisk.  So if a user creates a NetBSD partition
with something like pfdisk, and then runs the install script, one of
the suggested geometries is through the roof because the cylinder
geometry has been translated to the LBA geometry but the number of
cylinders didn't change accordingly.

Of course, arguably the install script should just make up something
out of whole cloth for the disklabel it installs, unless the user
intervenes.  Then the previous disklabel geometry would be irrelevant.
(You don't want to use the BIOS geometry for the disklabel because FFS
will typically demand something like 4K fragments if it thinks you
have cylinders that huge.)