I guess some Ambisonics zealot added this without knowing much about Vorbis I
the point was that the ambisonics suggestion in the 5.1 for Vorbis I bounty wiki entry -- quoting "This should be implemented with ambisonics as the internally coupled channels, and then use ambisonic g-format filters for en/dec coding from and to 5.1. This will allow correct playback on many different speaker layouts and an easy path to headphone support." -- just doesn't make any sense because the Vorbis I spec doesn't support this.
- What resources/documentations/specs should I read
Sorry, I don't see any relevance to what I said. Are you just being informative or did you try to point out a mistake/misunderstanding of mine?