The article doesn’t say that. It says that most arent spending above 43% on housing. It doesn’t dig into that, likely on purpose.
https://archive (dot) is/2024.05.08-164727/https://www.economist.com/finance-and-economics/2024/04/16/generation-z-is-unprecedentedly-rich
If your balcony could support the load you could grow quite densely with hydroponic towers, but you won’t ever recoup the costs. That method is also very little work beyond the initial compared to soil.