John Paganetti once said „There are no u documented functions when you work for IBM“.
many of us are using those functions and we figured out their signatures. Some undocumented stuff is also used in shipped templates.
I no longer insist in making all of the undocumented stuff documented. At least, give best effort support, if we run into issues. Do not block us at L1. We are using the stuff, and we know about limitations. Do not treat us as „citizen developers“ any longer.