Some of that matching is just for diameter, and some of it is for overall heating capacity.
In general, for a narrow cook pot you need a narrow flame pattern. For a broad cook pot, you can probably use a broad flame pattern. If you have a cook pot with a volume of only 600ml, then maybe you want some burner that is small. If the cook pot is 1.5L, then maybe you want a big burner.
If I am only boiling water in a 600ml pot, then often I will take only Esbit. If I am trying to cook something carefully in a big pot, then I take a 12-10 burner with a simmer adjustment on it.