Actually, it is a lot worse then that.
Food trades for the same base price as minerals.
The miner's base upkeep is 2U so he is making +2 a turn of "profit". The farmer has the same upkeep (2U) so he is making +4 a turn of "profit". If we are looking at it per worker it is important to observe that if we factor in % bonuses to production the gap between 4 per miner and 6 per farmer gets bigger - because upkeep stays the same yet you are adding % bonuses.
If both get +50% bonuses, miner is making 6 per turn (so 4 after upkeep) and the farmer is making 9 per turn (so 7 after upkeep) and it doesn't get better for the miner as we get deeper in the game.
With either Agrarian as a trait or the Galactic Trading Hub, making food and selling it is just as efficient as making energy and you can do things with it you can't do with energy. If you have both, you can pretty much make food, sell it, and buy minerals and be as efficient as mining, or very close. On the other hand, selling minerals to buy food is silly. It also usually bribes AI's better then minerals and energy in early game. There is also no Dyson Sphere or Matter Compressor for food or way to "trade" it into existence.
If we just go by production per worker, your right. If we go by "what can I trade it for or make it into" it is very unclear.
You can also directly trade food for population, which is rare with energy and impossible with minerals.
How about I put .5 - 1.5 in for food and put a * next to it and leave a note that it is a bit messy?