Table short name and queries

You cannot use short name in $table.
$table is a table name.
'mailing_suggestedchanges msc' is not a table name.

You are confusing the Model and QueryBuilder.

The CodeIgniter’s Model provides convenience features and additional functionality that people commonly use to make working with a single table in your database more convenient.
https://codeigniter4.github.io/CodeIgnit...tml#models

ci-phpunit-test | CodeIgniter Testing Guide | CodeIgniter 3 to 4 Upgrade Helper