The specific post you cite is a very old post from 2012, that very roughly indicates the criteria for which questions would be migrated to the new Meta Stack Overflow once the split happens.
However, a much later post published as the split was about to take place mentioned that only recent and unresolved Stack Overflow-specific questions would be migrated. The question you cite had already been resolved earlier and was posted three years before the split, so it didn't meet those criteria and wasn't migrated. To quote from that post:
However, please do not [request migration] just for the sake of bucketing or sorting content - unless it's very recent and seemingly unresolved, we'll probably decline.
It's also worth noting that questions older than 60 days cannot be migrated by normal users; I suggest reading the reasons why that is the case. While it technically is possible for Stack Exchange staff to bypass this policy, it is very rarely done except under exceptional circumstances.
We are currently in the process of closing older Stack Overflow-specific content that wasn't migrated; as there are a lot of these questions laying around, and as doing so is not an active, urgent priority, it takes some time.