Comment # 1 on bug 981004 from Marius Tomaschewski

(In reply to Jan Engelhardt from comment #0)
> When a package is uninstalled, it will also be removed from the boot
> sequence, by means of %preun generally calling %service_del_preun
> foo.service, which expands to (among other things) `systemctl disable
> foo.service`.
> 
> To disable template instances such as foo@bar.service and foo@baz.service,
> one can - and must, since "bar" and "baz" are not known at any time to the
> package management system - use `systemctl disable foo@.service`, which will
> disable all instances.

FYI: All this is applicable for non-static services only (having an [Install]
section) and calling enable/disable on them causes errors IMO. The macros do
not catch this.