Agree in general, but note that Java itself does not follow this rule: StringBuilder's and StringWriter's toString methods use toString for behavior — creating a string from accumulated chars, and I'm fine with that.
That said, it does seem like Microsoft has since moved away from overriding ToString for such things. In all honesty, Object.ToString was probably a mistake to begin with.
Any form of (semi-)automatic SomeObject -> String should be treated as a convenience for the developer to avoid getting a non-descriptive memory location reported.
Having the automatic toString isn't the problem, but maybe the name of the method is. It could be called "asDebugHelpRepresentation" or something more descriptive.
Whereas in the general case, where code can be sparse and types can be more freely altered, you could very easily change the type of something and not realize that a ToString() call on that type lurks somewhere else in the code base.