>>23105519Special split = gen 2. Physical/special split = gen 4. Get your terminology right.
Gyarados is a very unusual case anyway. It used to be a 580BST mixed attacking monster in Gen 1 that was only dogshit competitively because of omnipresent Thunderbolt. Gen 2 saw it heavily nerfed with SpA dropped to 60, and though it finally got usable flying STAB (HP Flying), it was still forced to go mixed due to barren movepool, and was even more so unusable in OU.
Getting Dragon Dance and EQ finally made it usable in Gen 3 (though its movepool was still very barren). Became an OU staple after physical/special split in Gen 4.