Is "install-new" and "clean-system" necessary on each update?

The problem Iim having with this is that slackpkg clean-system shows all packages Iive installed with slackpkg+ from other repos to be removed, too.
But if I blacklist them, they wonit get updated either.

Is it even necessary to run those commands on a normal update, or do packages only get added/removed in a new release?