It was reported that watermelon is indeed the evolution food for pachys to citrullus.
Also the wiki page was edited and saruta orange is apparently the ake ome shop item. I didn't see any confirmations on this yet.
If it's true, it makes a little more sense why it was added as a food. Ambrosia and Amrita though, who knows. It makes me think what if they added them to skip certain monster evolution phases like how savory shank is used on behemoth? You would think that would have been announced in the patch notes though.