There are statisticians and then there are ....

On-time arrival numbers at an airport is a function of:

(1) airline operations (were they delayed at the origin?)
(2) weather at airport (ORD sucks compared to DFW for this)
(3) En-route congestion
(4) ATC congestion around the airport
(5) Ground traffic congestion
(6) Gate availability

It dneither measures nor correlated with congestion at the airport. One airline may have better on-time arrival performance at the same airport than another airline during the same day depending on their operations and where they are coming from. For example between ORD-EWR, traffic is frequently delayed due to storms enroute while the traffic from the West has no delays.

Interesting statistics above but if that is supposed to imply something about whether WN would find getting in and out of DFW easier or more difficult than WN flying into another airport, then it wouldn't be from a statistician.