when the books and everywhere say that when you undo the spring plate its meant to do it quite violently yet mine had to be pulled down and off? the bar is solid so its not broken but yeh im mystified as to why id didnt go ping! when i undid it and popped it up over the bit it sits on.

It may not have been "resting" on the stops in the first place. If you had a lowered or sagged rear end in the first the spring plates would not be resting on the stops with much pressure.

Does that make sense?

Yes the sagged theory will make sense - also for bugs that have already been lowered in the rear won't have the same amount of tension built up.