Dark Grepher & Dark World

People, i hear that Dark Grepher don't work using Dark World, both effects are costs, so if i discard any Dark World using Dark Grepher it's effect will not activate.
But that's valid to OCG and TCG?

Should be in the rulings section.

Yes, Dark Grepher's discard is a cost and won't work with Dark World.

Why would it be any different in TCG or OCG...