Banana plantation on plains yields no production (hammer)

Is this as intended? Messing about as Haile on a terra map and started in jungle. My city, Harar has 2 banana plantations on plains. I don't usually drop plantations so early on jungle/bananas but I have oral tradition pantheon bonus. I'd not noticed this before and I guess I noticed it now since it's "early" and I'd really like that production.

Banana plantations add 2 and subtract 1

That's intended.

Where would I find out it's intended? Why don't citrus plantations remove production?