I think it's a lot expect people that contribute to always have done the work on both PostGres and Oracle. It is significantly more work to maintain both environments and test each one as well. It makes the barrier to contribute much much higher.
I'd favor a process where things were clearly labeled "not ye t tested postgres" or "not yet tested Oracle" and then other people can grab that work and complete. It's actually a really great project for newbies to grab something that works in one database and make sure it works in the other.
