In the osx simple preference, when Disabling OSD title are still shown. I didn't investigate much, but I guess --disable-osd doesn't disable title show.
I finally get what you mean. Fixed (sha-id: 86c7e74f) by checking value of config variable "osd" in function DisplayTitleOnOSD() (file: src/video_output/video_output.c). On commandline this would be: --no-osd or --osd options.