PS5 uses DNS to resolve where to send RTMP stream. The author found out that they cannot spoof the main server since that server uses TLS and it's not possible to make the PS5 trust self made certificate. The author then runs a real Twitch stream and monitors DNS requests and finds DNS of the server that receives the RTMP stream and spoofs only that final server. It's more of a problem with RTMP protocol/Twitch security rather than the PS5.

If sony wanted the ps5 to only send to twitch, they could absolutely enforce TLS authentication of the server, but they don't, so i guess send your video wherever.