Parabellum you make a good point – using contingency fuel on taxy when the delay could be predicted might well be poor judgment. However, there are reasons, as BOAC said, when the delay is unexpected and more thought might be required as to the merits of getting airborne or taxying back. Things in aviation are rarely clear cut.
However, typically, life is very black and white for 411A and predictably, he delivers his usual unthinking and simplistic type of answer…..