So if you arrive at destination, are given "no delay" and you have min fuel, or even your massive 600kg contingency!
My point is: are you going to use 19 mins of fuel to hold if you can't be assured of landing at destination? Semantics I know, but I'm just making the point.
You might also note in the AIC:
The information concerning delays that is passed to the crew by the controller is the best available at the time and takes account of
the expected volume of traffic at the aeroplane’s estimated arrival time.
For the final time, I say again that I don't carry the 20 mins on every occasion. I do, however, believe that the way the AIC is written means you can justify the extra fuel if you want it.