Exactly - an unexpectedly long taxi time (or any other unexpected delay between engine start and reaching the runway hold line) is a contingency, for which the contingency fuel is available and intended.
It does mean that if there are additional contingencies once on the air (everything goes fruit-shaped: unforecast headwinds, 100nm diversions around weather buildups), that the contingency margin will be less, so keep it in mind as the flight progresses.