We read
       -f     Force removal of symlinks even if /etc/init.d/name still exists.

However we find that indeed you might as well change that to

       -f     [no-op, retained for backwards compatibility]

or
       -f     Force removal of symlinks even if /etc/init.d/name still
       exists [enabled by default]

Proof:

# sysv-rc-conf  --list cron
cron         0:off      1:off   2:on    3:on    4:on    5:on    6:off
# update-rc.d cron remove
update-rc.d: using dependency based boot sequencing
# sysv-rc-conf  --list cron #GONE:
cron
# update-rc.d cron defaults
update-rc.d: using dependency based boot sequencing
update-rc.d: warning: cron stop runlevel arguments (0 1 6) do not match LSB Default-Stop values (1)

[CCing debian-init-diversity which is planning to adopt insserv ttbomk]

The -f parameter is mostly just passed along to insserv and causes it to
ignore any potential dependency errors afair.

If you could remove cron without issues, then this means no other
service had a hard dependency on it.

At least that's how I understand the meaning of -f.
Felipe, is this correct?

If so, I guess the correct fix would be to update the documentation of
the -f flag accordingly.

Right. It is only passed on to insserv. Therefore it only has meaning when
initscripts is installed.

Agreed.

On Wed, 14 Nov 2018 21:21:25 -0300 Felipe Sateler <fsateler@debian.org> wrote:

Jesse, as maintainer of sysvinit/insserv, do you want to submit a MR for
this?

Michael