Yes I understand this, here's my 2 cents,
As Plesk have some limitations with MariaDB versions higher than 10.3, there will always be a risk of an update coming from MariaDB developers..
And I don't want to turn off automatic updates, therefor, to reduce the risk of unwanted breaks in servers, why not Plesk team create a repository for MariaDB and when new version comes up, the team tests it then includes it in the repository..of course if there are no legal issues ... just a suggestion though.