Yes, but we also live in a world which doesn't have such magic. If we lived in a world where simple, everyday tasks and items could literally be enchanted for a function, do you think that it would be that unreasonable of a thing to say, especially considering the person holding the staff appears to have easy access to a vast array of magical resources?
Yes, it's an absolutely reasonable assumption in the real world that something like that uses simple mechanical devices, rather than some advanced technology that may or may not be indistinguishable from magic. But Flipside does not take place in our world, it takes place in a world of magic, sorcery, and far lower technology and manufacturing capability than ours.
Also, It's doubtful that you'd be able to make a staff like that with springs alone - to have one of that length, to move with that speed, you'd need a very strong spring, and you'd need to either crank it back by hand, or have a motor inside that pulled it back in, and it wouldn't move with the speed shown of Danzig's staff. You would also be able to have a spring system that both expanded and retracted the staff, by launching a weighted end out and locking it, so that when you pressed another button to release the lock, it would use the tension from the extended spring to come back, rather than the compression to spring outward - though It would be very hard to do on that scale - hell, it's hard enough to do on the size of a walking stick, let alone something that looks to be longer than a polearm.
Also, it wouldn't be able to pull back in a quarter or half of the way, and then pop back out again at speed on a spring system alone - on a spring, you'd have to retract it all the way to "Re-cock" the staff, as it were, and unless you had some sort of locking mechanism, it would just compress on impact - in other words, it would be an all or nothing deal - all the way in, or all the way out, nothing in the middle.