Kubuntu minimal install is converted to full install when upgraded to 18.10

1) 'lsb_release -rd'
Description: Ubuntu 18.04.1 LTS
Release: 18.04

2) 'apt-cache policy ubuntu-release-upgrader-core'
ubuntu-release-upgrader-core:
  Installed: 1:18.04.28
  Candidate: 1:18.04.28

3) What you expected to happen
A user who chooses the "minimal install" option introduced in Bionic Beaver expects that an upgrade to Cosmic will retain the minimal package set.

4) What happened instead
The release upgrade for Kubuntu 18.04 to Kubuntu 18.10 installs applications not included in a minimal install.

5) Background
After reading the experience of two users in
https://www.kubuntuforums.net/showthread.php/74565-How-do-I-update-while-maintaining-a-minimal-desktop, I checked this myself as follows:

I downloaded the Kubuntu 18.04.1 iso
installed it using the minimal option in a VM
ran sudo apt update and sudo apt full-upgrade
rebooted
changed software sources to notify of normal releases
ran sudo do-release-upgrade

When I chose to view details at the "Continue [yN] Details [d]d" prompt, there were the following lists of packages:
"No longer supported:"
"Remove:"
"Install:"
and
"Upgrade:"

Of the four, the "Install:" list contained packages such as
akregator
cantata
kmahjongg
kmail
kmines
knotes
kontact
konversation
ksudoku
libreoffice-base
libreoffice-calc
libreoffice-draw
libreoffice-impress
libreoffice-math
libreoffice-writer
just to list a few well-known packages.

In effect, the upgrade of a minimal install option of Kubuntu 18.04 to Kubuntu 18.10 converts the system to a full install of Kubuntu 18.10. The same procedure works as expected for Ubuntu and Ubuntu Mate which both retain the "minimal state".

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: ubuntu-release-upgrader-core 1:18.04.28
ProcVersionSignature: Ubuntu 4.15.0-39.42-generic 4.15.18
Uname: Linux 4.15.0-39-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.5
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: KDE
Date: Sun Nov 18 17:45:26 2018
InstallationDate: Installed on 2018-05-02 (199 days ago)
InstallationMedia: Kubuntu 18.04 LTS "Bionic Beaver" - Release amd64 (20180426)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
Symptom: ubuntu-release-upgrader
UpgradeStatus: No upgrade log present (probably fresh install)