>> Ogg is just a container format and can contain a multitude of audio encodings

> Only Vorbis should be used in .ogg files.

Not everybody seems to share your opinion (from the above link):
"Ogg was intended to be, and usually is, used with the following Xiph.org free codecs: [...] Speex [...] Vorbis [...] Opus [...] FLAC [...]"