AFAIK it wasn't in the leak (that "YT" platform specifically). Also, open-sourcing proprietary projects of this scale is a pretty hard job and it can't be done quickly — seems they had been doing it for a long time, starting long before the leak.
It's truly a hard work, because we were very tightly tied to the Yandex infrastructure and we had to learn how to deploy in k8s from scratch. Also you need a new brand and clean your documentation from irrelevant things... All this takes months.