It's throughput vs latency. A walking person takes up more room on an escalator vs a standing person so an escalator full of walkers moves fewer people per hour than one full of standers (worse throughput.) However,\ each individual walker will reach the top faster than if they were standing (better latency.)

There's a similar phenomenon with cars. Imagine a single lane road where all cars travel at the same speed with each car maintaining a following distance of s^2 / 200 ( s is the speed in km/h.) If the road is 10km long, the time it takes travel the length of the road is simply 10 / s - i.e. driving faster always takes less time for a single driver (better latency.) However, if you were stand at a point by the road and count the number of cars that pass you per hour it would be s / (s^2 / 200) = 200 / s - i.e. the number of cars that can use the road decreases the faster each car drives (worse throughput.) This is one of the reasons why lowering speed limits can actually improve traffic, although in real life there's other factors at play too.