The two formats are similar, but distinct. There is an explanation in the pinned introductory post.
TL;DR: In a NoSafetySmokingFirst, the text reads correctly left to right, but visual cues lead you to read it top to bottom. In a DontDeadOpenInside, the text reads correctly top to bottom, but visual cues lead you to read it left to right.
The two formats are similar, but distinct. There is an explanation in the pinned introductory post.
TL;DR: In a NoSafetySmokingFirst, the text reads correctly left to right, but visual cues lead you to read it top to bottom. In a DontDeadOpenInside, the text reads correctly top to bottom, but visual cues lead you to read it left to right.