two mounts a go I was in one dealership in MO. the techs were working on brand new daycab cascadias. I asked them what's the problem and they told me trucks came in, they started them and after 20 min coolant went down to oil pan on all 3 trucks. they were changing head gaskets on brand new engines.
there is a guy here how is DD platform engine's certified tech . He told me that every week you can see a low mileage truck with broken rod and block towed to dealership. Some of them has less than 10k m. These problems happen because all bolt are loose. No assembly quality control at DD plants. Sounds crazy but if you buy a brand new engine you need to take off the valve cover and torque all head bolts, all bolts under cover. After that you need to drop down the oil pan and torque all rod and main bearing cup's bolt to avoid broken rod/block ugly situations. i know sounds crazy but no other option. Downtime is lost money.
You can bet that they will not tell the new owner and down the road the he will wonder why he is having so many weird problems. It looks like you did the right thing without a doubt. We can all benefit from your situation and the advice given by those who know.