In case of the Foo::Bar subclassing/wrappig Foo, you as the author of Foo::Bar are in a much better position to forward the blame. You can't expect users of a "::Simple" wrapper to dissect the wrapper and guess all the preconditions and assertions you, the author of the "Foo::Simple", made about the "Foo" to find out whether there's something wrong with Foo or with the way you use it. And even if the problem is inside Foo, you usually do care. Even if the only thing you can do is to close it with "problem is in Foo, it was reported a year ago already".
Regarding the other case ... if you can't be polite, don't be impolite. Just close the bug selecting "N/A" or similar reason.
Enoch was right!
Enjoy the last years of Rome.