This is hopefully just a weird mistake someone made... but I'd thought I'd report that I just (as in 10 minutes ago) got offered 12.13 and downloaded it to install 12.12.
False alarm, sorry! Just testing something and it escaped into the wild 
But eh .. today it is still there then. After trying to locate this 12.13 on the beta site I Googled for 12.13 to get to this thread
12.13 was going to come out eventually and now has. 
Yes, I just noticed, but could not delete / edit my post anymore. Ahum ..