No, you misunderstand. Silver (My Eevee OC) has two variants. One's the canon version for the Eeveelution Squad (no, not the one by PKM-150. See
imgflip.com/m/Eeveelution_Squad for more.) and one's a version that's usable in official games. That's this version. Did you read the comment in the img I linked? Also, Gen 3 (where I caught him) has glitches that enable you to make fully legal Pokémon of any species available in that game.