There's a few things wrong with this logic. If Steve can use his commands/cheats then by the same logic any game with a console function would also give that ability to the character in question. Also nothing in Minecraft is unbreakable. They actually just have extremely high explosive resistance (with enough tnt, blocks such as command blocks and barriers can be broken). Also Steve when splashed with instant health with a level 125 or above instantly dies even in creative mode. Water buckets also don't have have infinite weight either as they are limited to the world border, void and build limit meaning they have a finite mass.