Disclaimer: I am also
very skeptical of the whole concept of vertical farming, but...
That 5 hectares of land per person metric is totally inapplicable here. Sort of the entire point of vertical farming is to be (in theory) vastly more efficient per unit of land. If you believe the claims it's somewhere between a 10 and 50 times reduction in land usage for same output.
5 hectares is also on the very high end for estimates of that metric. It also drops hugely if you're not relying on animal products.
I don't think vertical farming in apartments is the future, but I think your calculations here are also way, way off.