I have found PIECES of rusty coils (they are not springs) in waterpumps. When the coil is in good shape (no rust) there is no danger to the waterpump, but when it starts to disintegrate thats another story. Always a good idea to use stainless.
I am another person who has SEEN the lower hose (and it wasn't an old worn out hose) collapse while simply winging the throttle from the engine bay. I believe a poor-flowing radiator can contribute to the problem by allowing the WP suction to build trying to suck coolant from a radiator that doesn't want to give it up.
Like putting your hand over a vacuum cleaner hose, the forces on the hose are FAR greater than with the hand off.