I get what he’s going for and people can split hairs over what “afford” means, but that’s honestly pretty lackluster advice. There are tons of moments where you simply don’t need two of something so you don’t form your budget to reflect you buying two of them - doesn’t mean your budget is now suddenly terrible and stupid. You drafted your budget to match your costs.
Someone would be stupid to hold off on chemo simply because they’d start scrapping the barrel if they doubled down on treatments. Opting to not buy your first car is pretty foolish if in your head you’re worried about what your saving would look like if you suddenly purchased two of them. Even something small like a daily drip coffee is subjected to this.

Complex things like what someone can reasonably afford shouldn’t be distilled down to one sentence pieces of advice.