Alright, here's what I got back from Tesla in response to my query from a few hours ago:
"Thank you for contacting Tesla Motors. I have forwarded a case to your local service center for visibility of replacing the adapters. If you have one of these NEMA 14-30 adapters and regularly use it, you will receive a replacement from us within the next couple of weeks. If you do not regularly use it you will receive a replacement as soon as possible. Until then, we ask that you stop using your current adapter, and that you instead charge your car in a different way, such as with a Tesla Wall Connector or NEMA 14-50 adapter (if you have one), or by Supercharging."
I am not sure exactly what "for visibility of replacing the adapters" means (remembering I asked them about both NEMA 10-30 and 14-30 adapters). The rest of the message appears to be a cut-and-paste of what was in the original email sent to owners. So I'm not sure if I accomplished or learned anything by this email.
(As an aside, "[my] local service center" isn't very well-defined for Bay Area owners, though they can figure out which one I go to the most often.)
Bruce.