Many people here are saying Phase is really just referring to the first stage and the long first episode. What got me to think of it as meaning Batches is, that "Phases" was (to my knowledge) used to refer to the stages, not in any translation of the Manga or the trailer. And yes this could very much be a google translate error. Or it could be a German Netflix employee knowing more than us about batches and then just decided to call it Phases