It may, but source says "You will need: Means for focusing a good few percent of the Sun's energy output directly on the Earth.", then posits using mirrors to do this. Mirrors could get Earth to something approaching 5800 kelvin, but that is nowhere near "a few good percent of the sun's energy output."
The sun has surface area of 6 x 10^18 m^2. Earth has surface area of 5 x 10^14 m^2. Earth can not be bombarded by more than the ratio of these to numbers with solar radiation using only mirrors. <<1 percent.
I see what you mean, but it seems like a self-correcting problem. Focus enough of the sun's energy on Earth, and it will be shrouded with a rapidly expanding ball of hot plasma, at which point its surface area would be much greater. Now you can focus even more of the sun's energy on it without conjuring Maxwell's demons.