These kind of arguments are silly since Sakurai tends to ignore other ganmes rules in favor of what makes a fun game. Almost everything about Lucario in Smash was made up not based on the games or anime.
What? You could argue that he isn't absolutely strict at all times, but to say he "tends to ignore" game rules? Pretty much the exact opposite happens. Have you noticed, for example, how each and every Pokémon doesn't have more than four actual game moves (as in, properly named)?
Pikachu: Skull Bash, Quick Attack, Thunder, Volt Tackle
Jigglypuff: Rollout, Pound, Sing, Rest
Pichu: Skull Bash, Agility, Thunder (quite fittingly, only 3)
Mewtwo: Shadow Ball, Confusion, Teleport, Disable
Charizard: Flamethrower, Rock Smash, Fly, Fire Blast
Squirtle: Water Gun, Withdraw, Waterfall, Hydro Pump
Ivysaur: Bullet Seed, Razor Leaf, Vine Whip, SolarBeam
Lucario: Aura Sphere, Force Palm, ExtremeSpeed, Double Team
While, sure, there is often some rule-breaking (like Pokémon saying their names, or made-up moves like "Thunder Jolt"), it's obvious that Sakurai is well aware of the canonical context of each and every character move/feature in the game.
I'm pretty sure Mewtwo can mega evolve in the anime by itself.
Although the anime (and particularly M16) isn't the best source when it comes to mechanics, this is a fair point. Especially considering that in Melee, Mewtwo was mostly based on his anime counterpart.
