He was right to wait
Disaster could have been averted had he said something earlier but like he said it was not his department. As long as the job was being done then not his business to complain how they do it. However after the disaster he was completely correct to set the boss straight. Right for the company and right for his own work not being wasted. It's disrespectful if he is working hard and others are slacking off and putting his work at risk.