Comment 13 for bug 1890263

Thanks everyone for the discussion so far, I'm trying to add a few details and fill a few argumentative gaps.

First let me re-share the simple scenario which I used to illustrate/prove the issues.
Then in another comment below I'll outline a few affects of this overall case.

Example:

On bionic install it "wrong" not using the meta package
$ apt install apache2 libapache2-mod-php7.2
$ do-release-upgrade

Before:
# dpkg -l | grep -e apache -e php
ii apache2 2.4.29-1ubuntu4.23 amd64 Apache HTTP Server
ii apache2-bin 2.4.29-1ubuntu4.23 amd64 Apache HTTP Server (modules and other binary files)
ii apache2-data 2.4.29-1ubuntu4.23 all Apache HTTP Server (common files)
ii apache2-utils 2.4.29-1ubuntu4.23 amd64 Apache HTTP Server (utility programs for web servers)
ii libapache2-mod-php7.2 7.2.24-0ubuntu0.18.04.11 amd64 server-side, HTML-embedded scripting language (Apache 2 module)
ii php-common 1:60ubuntu1 all Common files for PHP packages
ii php7.2-cli 7.2.24-0ubuntu0.18.04.11 amd64 command-line interpreter for the PHP scripting language
ii php7.2-common 7.2.24-0ubuntu0.18.04.11 amd64 documentation, examples and common module for PHP
ii php7.2-json 7.2.24-0ubuntu0.18.04.11 amd64 JSON module for PHP
ii php7.2-opcache 7.2.24-0ubuntu0.18.04.11 amd64 Zend OpCache module for PHP
ii php7.2-readline 7.2.24-0ubuntu0.18.04.11 amd64 readline module for PHP

After:
# dpkg -l | grep -e apache -e php
ii apache2 2.4.41-4ubuntu3.11 amd64 Apache HTTP Server
ii apache2-bin 2.4.41-4ubuntu3.11 amd64 Apache HTTP Server (modules and other binary files)
ii apache2-data 2.4.41-4ubuntu3.11 all Apache HTTP Server (common files)
ii apache2-utils 2.4.41-4ubuntu3.11 amd64 Apache HTTP Server (utility programs for web servers)
ii php-common 2:75 all Common files for PHP packages

There are other variations of the bug, but they all end in a similar situation like this.

And with that situation PHP execution is essentially "off"