This is the cover for Sega Maga magazine, a Japanese publication. Just by looking at the cover graphic here, you wouldn't be able to tell this is their Sonic Adventure 1 issue...but it is! They're using an older (but still 3D rendered) Sonic & Tails without the SA1 look. Why? Maybe it's a very early preview, and they didn't have the art yet, or they had only the 'new look' flat arts & wanted to go with something obviously CG & 3D to promote the look of the game. But, if you look there in the black text (in the yellow circle) it is indeed SA1 related. It is interesting to see the non-matching art styles used for the cover.

This image in the gallary is here to help explain the cover above. Japan wasn't the only region to use some kind of non-matching-SA1 style or speculative type art in a magazine. This CG art of Sonic was likely done 'in house' at whatever magazine this was because it's got the concept of the look, but it's still pretty wrong. Long straight spikes, tiny simple shoes, big wierd socks, borderless ears & sort of wiggly versions of his green eyes & mouth. At least the Sega Maga used official CG to try and promote the concept of the first really non side scrolling nor isometric Sonic game that wasn't a racer.