I agree. After long (overnight) shipment there will be ammonia and CO2 in the bag. ammonia is much more toxic with high pH. In the bag unopened the CO2 will keep the pH down and keep ammonia from been too toxic. When you open the bag, CO2 escape result in increase pH of the water and increase ammonia toxicity.
After long shipment, If the fish seem OK in the bag I put the unopened bag in the QT for temperature equilibration. After about 10 mins or so the temp should be the same, I dumped the fish out and change 50% of the water. Then I check salinity. If the salinity is the same, I just dump him into the QT. If Salinity is significantly different, then I do a fast drip. 15 mins at the most and into the DT.
If the fish look bad in the bag, then I just dump him directly into the QT. The fish look bad because Ammonia, CO2 or O2 depletion. These problem need to be correct right away, to hell with salinity and temp.