WOW I didn't know this... always thought that was a distinct sprite art style created for this game carried from Panel De Pon

I suspect that the Yoshi art on the cover is a bespoke creation based on the original sprite art, because I can't find any other source for it. Other things I've noticed is the cover art uses a slightly different palette for Yoshi's body (green + lighter green instead of green + white) (1/2)

And the tip of the tail doesn't match the sprite art ripped from the game. In the actual game, the tip is obscured by the "O" in "Game Over". The cover artist likely didn't have the original sprite art handy, so they took some artistic liberties. (2/2)

Good find! Yeah this makes more sense given the sprite art is more professional looking than the illustration imo. With a quick look over I thought the sprite was translated from the illustration and not the other way around. The shading is pretty wonky

Now I think it’s possible that the cover artist had never seen a Yoshi before, only got a bad photo of the game over screen as a reference, and thought Yoshi’s body was very glossy and the white parts are highlights. That might explain the colour palette and weird shading.