• "The site needed to have at least 1000 open questions

• At least 70% of the questions on the site needed to have at least one upvoted answer

There is one exception we did make for a community, and that was on the Artificial Intelligence site."

There appears to be another exception: Drones & Model Aircraft has 648 total questions and therefore didn't meet the 1000 question requirement.

The post says:

For the sites that are leaving Beta today, the following criteria were determined:

• [...]
• The site needed to have at least 1000 open questions
• [...]

There is one exception we did make for a community, and that was on the Artificial Intelligence site. [...]

There appears to be another exception: Drones & Model Aircraft has 648 total questions (634 of which are open) and therefore didn't meet the 1000 question requirement.