If service file has <service name="set_version"/> there is
_service:set_version:$name.spec file which is made of $name.spec file and
version got from VCS.

When spec file is updated, service spec is updated too, but there is exception.
If package is branch of some other package and original spec file is updated,
then dependent spec file is updated but not service spec.

You can see example at
https://build.opensuse.org/package/show/home:NickLion:kde:unstable:extra/kipi-plugins5
There is kipi-plugins5.spec file which is updated by dependency, but
_service:set_version:kipi-plugins5.spec file is much older and has no changes
(you may look at line 29:
BuildRequires:  libkgeomap5-devel
vs
BuildRequires:  libkgeomap-kf5-devel).