Had exactly the same experience, and actually messed it up more than you did of which I'll spare you the details, let me just say I'm now at my third email account at Plex ๐คจ which is kinda weird since I'm a Plex user since about day 1 when they forked from XMBC (now Kodi). Not sure if that says more about Plex and how it works ... or me ๐
The only difference I see between the Binhex/Linuxserver docker templates is indeed that you have to fill in a claim code after retrieving it through https://www.plex.tv/claim/ after which you go through the Plex setup wizard to set a name for your server, add libraries and so on.
For the binhex/linuxsever dockers you never arrive at that, you just land in the Plex web app without a way to access the server.