...again, I don't see that it was discussed to include the SERIALIZE behavior to VERBOSE. I don't use SERIALIZE myself, but during our podcasts, Michael (CCing him) was wondering why it was so.
Summary: I haven't found explicit discussions of including new options to VERBOSE, when that new options were created. I used Google, the .org search, and postgres.ai semantic search over archives involving pgvector/HNSW – I might be missing something, or it was really not discussed when new options were added.