I’m sure a noodle would do the same thing… but here are a few differences.
A tipdown will have about 2-3 feet of travel at the same resistance to the fish (virtually none), a noodle would be about 6″ before it hits backbone and the fish feels it.
A tipdown would be easy to see from 30-40 yards away when a light bite happens, I know I couldn’t see a noodle tip from 40 yards away.
Tipdowns are cheap if a big catfish or something grabs it when you are far away, a noodle rod + reel is a heck of a lot more expensive!
Tipdowns count as tipups (at least here they do) so we are allowed 2 rods plus 3 tipdowns on the Miss river. A noodle in a rod holder is counted as a rod.