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The article mentions the Super Game Boy 2, but only in an "Aside" box.

The main point is that the original Game Boy runs at 4.19 MHz, while the Super Game Boy 1 runs at 4.30 MHz, or 5.12 MHz if the game calls an undocumented API. (At least I think that's the main point of the article; it's only stated implicitly in the numbers.)