The video PLL circuit is only present in home consoles, it was added as a way to improve composite video quality by adjusting the main clock frequency with the color burst frequency.
DIVO and REF are compared to generate the adjustment voltage for the varicap diode.
It was added during the production of first generation AES consoles as a correction board wired to different locations on the main board.
The divider was made using 74LS161 4-bit counters.
Board's reference is PL241S ?
When SNK made the second generation chipset, the bodge became part of the system with the inclusion of the divider logic in LSPC2-A2.