Recaps are only to be added if the format is different from the original (Example: TV to Movie).
Other than the aforementioned format change, recaps are accepted under the condition that it is intended to be part of the series’ total episode count.
Re:CREATORS has a recap episode as its 13th episode that counts towards its 22 episode count. However, in 3-gatsu no Lion Recap (MAL), episode 11.5 is not a conventionally numbered episode, as denoted by the “.5”, and thus not counted toward its total 22 episode count.
Some titles will refer to these X.5 episodes with titles like “intermission”. In cases like these, they still will not be added to AniList.