<<Or the dicey conditional clearance "behind landing aircraft on final, line up and wait"...>>
Absolutely nothing "dicey" about this procedure, which I've used hundreds of thousands of times (although in the UK we now say "after...")... but...
<<'Line up and wait behind the landing aircraft' is a commonsense procedure and poses no danger >>
Is immensely dangerous.
Why don't pilots use the correct phraseology?