actually it looks like the resistor is there on the sync line in the gray shrink tube before the cap.
And yeah I see only resistors on the RGB lines, and like you said, according to this page it needs resistors and caps. And maybe for pal mega drives only? As my cable from retro_console_accessories on ebay which I use on my NTSC Genesis has only caps on the RGB lines, no resistors. dont have an ossc so who knows if it works with it or not.