AFAIU C++ will require that you initialize the members inthesameorder as defined. It also won't permit you to exclude any definitions. Why even bother?
Somewhat controversially, C permits you to define members multiple times, with the last definition taking precedence. Compilers sometimes warn about this, but I've personally found the behavior useful--I'll write an API that provides a macro with default values yet which allows the user to override any particular definition. I don't think I've ever had a bug in an initialization, at least not involving multiple definitions. That seems like a very easy and superficially useful diagnostic to write, but which prevents useful behaviors; behaviors that named initializer's were deliberately designed to provide.
In a C++ designated initialization, members may be omitted. (You were told wrong.)
There is probably no reason to enforce order unless unmentioned elements have a non-trivial destructor, so that could be relaxed in a future Standard. Members that need destruction would need to be destroyed in the opposite order; enforcing order allows reusing code already generated for the containing-object destructor, but in many interesting cases (e.g. C structs) there are no destructors to run anyway. In the others, there is no reason why it would need to re-use the class destructor.
AFAIU C++ will require that you initialize the members in the same order as defined. It also won't permit you to exclude any definitions. Why even bother?
Somewhat controversially, C permits you to define members multiple times, with the last definition taking precedence. Compilers sometimes warn about this, but I've personally found the behavior useful--I'll write an API that provides a macro with default values yet which allows the user to override any particular definition. I don't think I've ever had a bug in an initialization, at least not involving multiple definitions. That seems like a very easy and superficially useful diagnostic to write, but which prevents useful behaviors; behaviors that named initializer's were deliberately designed to provide.