I have no idea why IBM bothered including a solenoid on those things, the beam spring is more than enough to let you know that you've pressed a key! Perhaps it was to do with making the user aware of potential electronic failures with the keyboard.
The LK-201 I've used (with a VT-320) didn't beep. Perhaps it needed to be set up in a particular way? But either way, the keyboard on that thing is a nightmare.