LOL yep....I think that all that PCB is doing is:
RGBS to s-video / composite video conversion
Rapid fire
Sync deflection for horizontal adjustment
It seems to be just passing RGBS, untouched, straight from the jamma edge to the 8 DIN connector. This is perhaps why they have the statement that it's designed for professional monitors and not household televisions. This is really BAD for people hooking these things up to consumer televisions.
I'm drawing it up now but basically the RGB from the JAMMA edge goes to the din connector then to that encoder. So it's literally doing nothing but adding a pot to do horizontal adjustment.