In the same way that JJ2+ is cheating at multiplayer. Sure, it can be used to do /maxscore 5 then /bluescore 5 or something, but it's generally not used for that because cheating isn't really that fun. I think a large amount of the fun would come doing just the opposite, and increasing the difficulty by removing carrots or powerups or reducing the amount of health you have. Also, the trigger commands would be a nice feature for testing levels out. The level cycling commands usefulness should be obvious. Somethings like extended TNT range could potentially allow for single player levels that wouldn't work before. Some commands, like negative health from kills or frustration, if modified to apply to baddies instead of other players, could create some really unique gameplay. Instead of just having to stand back and mash the shoot button (which is boring and occurs in way too many levels) you would have to carefully avoid the enemies without being able to fight back.

So sure, it could be used to cheat. But that's not how I would be using it.