I know you can trade steam balance/games, but I see some locked posts here for game trades vs fg.

Is there any legitimate way to trade eShop balance, gift cards, or Switch games? If not... Why?

You must be able to gift in the same way that you can on Bnet and Steam for us to approve these trades. Last we checked, you couldn't digitally gift on this platform. See: https://forums.d2jsp.org/topic.php?t=84718992&f=385