Block time (airlines calculate it differently) was traditionally viewed from “block to block”, the time the wheel chocks were removed for the aircraft to move under its own power for departure to the time the wheel chocks were put back under the wheels at destination. Now it just means what the airline thinks the flight time will be for scheduling purposes.

As a passenger, this is what you see when your app tells you the flight time. It includes taxi out and taxi in.

Delay-prone flights are often over blocked, so a perfectly delay-free flight (push, taxi, takeoff, fly, land, taxi in, park) that takes say an hour and a half total might me blocked for 1:50 because historically one of the airports might be busy at that time an they know there will be a long taxi, gate holds, whatever.

So sometimes fate smiles on everyone and you get to leave early, miss whatever built in delays there might be planned, ATC gives you a couple shortcuts, a favorable wind, and bam, you’re in 30 minutes early.

So not really a speed run, just lots of luck.