From my reading of the article, he was the triage officer during the arrival of almost all the critical patients, and it was only after the acuity level started to drop off that he delegated to a nurse.
That said, I have never heard "black tag = not breathing = don't try to help"[1]. I know for a fact that the boundary for who to try to save immediately and who to deprioritize is very grey in many cases (it is why you should have an experienced doctor doing it). A common example why that equivalency is not taught in ATLS is the case of a boat capsizing in frozen waters. There may be many frozen victims who are not breathing but could still be very salvageable medically. If you chose to not help those who are not breathing in that case you would plausibly be found negligent without some extraordinary situation to justify yourself with.
Another example would be mass overdose on fentanyl, many are saveable but none would be breathing when you first see them.
1. https://en.wikipedia.org/wiki/Triage#Conventional_classifica...
I'm not sure where your understanding of triage comes from, but you're mistaken if you think respiratory status isn't the primary determining factor in black/expectant classification (in the US, there may be differences in other international systems I'm not aware of).
The vast majority of triage in US is done using the START system (or START-derived systems, like SALT).
Here is a graphical depiction of the START classification algorithm: http://citmt.org/Start/images/flowchart2.jpg