The main reason it isn't a hammer is because of how the hammer works; its an object that spawns over where the hammer's sprite would be. However, this object alone cannot trigger things, and making it due to via tagging it Pushable could lead to other problems, such as triggering things the player shouldn't be able to trigger at all. Not only that, but the hammer does not change depending on if you hit a wall or not, and there's no way to trigger things by hitting a wall with anything at all, and to make the player be able to hit a wall, it'd have to be sideways and then lose or hamper visibility of the button, as the hammer does not strike directly up or down, only ahead of the player. There's also the fact that when you hit something with a hammer, it gets destroyed, like with ? switches, while this wall mounted button can be reactivated after a period of time. With a hammer, its clear you crush something, but with Custom 1 activated objects, you rarely cannot activate them again. So far, everything a Custom 1 can trigger can be retriggered.
I also don't like floor touch triggers for this kind of thing, because it forces the player to activate it if they may not need to just yet. It should be something the player can trigger on command, and that's not so clear or controllable with a floor touch. It also feels kind of awkward to just stand on something to activate something like this. I mean, if you were Ground Pounding the object or something, sure, but not just taking a step on it.