If that’s an issue with the OF source, I’d open an issue on the OF Github repo.
As far as I understand it's not. In OF's forum I was told that OF doesn't use it's own RtAudio library any more, but the one installed in the system (at least on Linux), and the ofSoundStreamSettings class lets you choose your audio API.
At first, looking through OF's forum, I tried to compile RtAudio myself and replace some files in the OF libs/rtAudio directory, but the way I finally did it seems much clearer and logical to me, so I guess it's not a bug. But maybe you know better..