https://opensea.io/assets/ethereum/0x31385d3520bced94f77aae104b406994d8f2168c/11103
Using an paint dropper like in MS paint, one can see there is a subtle change of color in this bgan.
"The way this is dealt with is be assigning the highest ranked pattern when it is detected. For example, GRADIENT is the top rank, so a Glitch with GRADIENT patterns and STAIR patterns is ruled a Gradient."
Was thinking it could be stair too from the left side, but this rule makes it a gradient.