You’re right. Urban farming with sunlight is fine. My energy arguments only apply to growing under artificial light.

Is it? That seems like a poor use of space that could be dense housing, commercially productive, or a wonderful park.

It would be helpful to quantify "plenty dense" here. Paris has a population density of 21498/km2. Turning that around, that's roughly 46 square meters per person. That doesn't leave a whole lot of space for a potato plot if you're supposed to cook and eat those potatoes somewhere, too.