This is somewhat brute-force thanks to the surprising lack of good documentation for the Ogg headers. The only other option would have been some rather bloated library for a function that should be 25-30 lines at most.
The idea is to have more control on the game side instead of dealing with these formats in the backend, which was done for FMod because it already had the decoders implemented.
However, with OpenAL this setup makes no sense and only complicates future extensions that can be better handled at a higher level.