User blog comment:Meruemgungiplayer/A Case Against the emitted Nen Beast./@comment-32818639-20190503144045

In the unofficial translation, Kurapika's speech is about the snakes; he still says: "...ability users with parasitic forms that only the user [SM user, not the princes] can see uses a lot of energy to make normal humans unable to see it." In the following speech, then he talks about the GSB without connotation of them being conjured. The official translation seems to have been oversimplified, causing a mixture between the two thoughts of Kurapika.

Abengane's and Rihan's beasts have in common the property of removing other abilities, the best explanation is that they need to be conjured because Conjuration is the only category that can affix rules to a space and therefore allow to isolate the ability removed from the target or the exorcised. All the exorcists (Rihan included due to similar effect) use some physical space to which they transfer the exorcised ability (Hina too). So that's why Kastro's clone being a Nen beast is something dubious.