This was part of pr #17615 and got somehow deleted. The MVC classes in the component needs to end with the type to be inline with the rest of the namespaced classes. See #17614 for more details. For example the Articles model which has now the name Joomla\Component\Administrator\Model\Articles will become then Joomla\Component\Administrator\Model\ArticlesModel.
Additionally it ports back the MVCFactory code from the 4 branch.