All Method K spreads are actually Method 1 spreads.
(It's not true that all Method 1 spreads are method K spreads, however most are).
But since some pokemon are made by method 1 (Gift pokemon, prize pokemon, roamers), it makes more sense to search for ALL of your shiny spreads, including those for these pokes. Instead of just those for wild / stationary legendaries.
It really shouldn't make much difference in all honesty, but there could be a couple hundred extra spreads that are only Method 1, and not Method K, so it makes sense to find them all. :)