I have ordered Y LR as you stated. So I am waiting for the confirmation it will have LG 5L M50.There are only Model Y LR/P with the new LG 5L M50 out for delivery. That pack has about 79kWh. Not 82.
You are right, usable capactity should be 79 kWh, but i hope there is some buffer, as found here: Model 3 / Model Y - Batteriewiki / Akkuwiki.
That's why I wrote 82 kWh.
Sorry for misleading info.