If you have s3oc there's a base game eggplant that shows up, maybe added from a patch? Try that, I'll clone it and check next time I run it if I remember.
I think the basegame eggplant is the one you get from gardening opportunities that grows literal eggs.
When I thought about that I thought so too maybe, but I remembered seeing an eggplant in the thumbnail. I doubled checked, it's a purple eggplant, marked as base game.
Maybe they have to be integrated into the basegame to work as harvestable produce.
That purple eggplant is just a prop for one of the recipes. I think it's ratatouille.
My sims was able to purchase an actual eggplant at the food store register in China. And when returned home the eggplant is also plantable. (I have all expansions and store stuff installed so not sure which one added this item).