The taxi clearance was standard for that runway and quite clear. How they thought they were departing 31 is perplexing. As far as the Delta flight returning to the gate it depends on the speed of the abort, temperature and aircraft weight. If a high speed abort it’s normal to have the fuse plugs melt and deflate the tires. Both a tire and brake change are often required. A passenger statement that the abort was initiated 2 to 3 seconds after the takeoff roll started suggests a low speed abort but witness timelines are often way off.