I think this is somewhat correct. Given that the shirt you mention has shades of the same color in the overlay. However, in lufty's case, the pink overlay makes things different. It strikes me as a half-ass tattersall and the color combination makes it awkwardly standout/creates confusion within the outfit.
Because patterned shirts are considered more casual in the hierarchy of formality, coupled with the fact that PoW is an objectively loud standalone pattern, I think it would work best without a SC. And certainly better without a tie. That said, a pencil stripe shirt or even Bengal stripe is a much better alternative for casual, sans tie or SC look, IMHO.