Congestion is often handled via "stacking" aircraft in a pattern like you see in the image, separated for safety and timing of approach. There may well be other aircraft in the stack but not reported via that site or there may be just the one at that time. In either case, the apparent reroute suggests more than congestion.

(For the record: I am not a professional pilot but I have flown and have family who are commercial aviators going on some 40 years.)