Some repeated tasks at every update

[Fergus Daly]

There are 12 tasks never shown ".done" in /etc/postinstall/ (6  .dash and 6 .sh) and therefore repeated at every update.
(Other users' installations might have 12 +/-.)
They are not particularly intrusive (though they can take a while) but nor is their inclusion or the exclusion of many others
at all obvious, except perhaps for *update* and maybe autorebase.
Not really too bothered about rationale but can an Admin confirm their necessary presence?