No, I've never heard of Bosch or BMW hiring shade tree mechanics to design engines. I'm relatively confident that this isn't a real issue.
I think your concern about weekend mechanics is also unwarranted because most of them aren't morons. The ones who are will be morons regardless and manage to destroy cars regardless.
I think your concern about weekend mechanics is also unwarranted because most of them aren't morons. The ones who are will be morons regardless and manage to destroy cars regardless.