You got the point, just go ahead and add as much data as you can/want, the original editor did not have access to this kind of information and left it empty for future editors to complete.
There is already a (long but interesting) discussion about entering audio dramas into the database, it even mentions the examples you are now interested in:
TL;DR: Use relationships for all people involved in the audio drama, the AC should include only the most important artists while staying close to the credits on the (front) cover. These are usually the writers, maybe also some important actors… At this point the interpretation of style guidelines and people’s opinions begin to diverge 