My read is that the NEC v Intel is arguing about the presence of the copyright notice, which doesn't affect copyright status, but rather whether you can collect statutory damages as well as actual damages. All creative works are "born copyrighted" these days.

As for the Hal Holbrook case, I could explain that as not wanting to dilute the value of the material. For example, if 1000 people started presenting the llama class for free, the value of having a certified Stonehenge instructor do it for hire would diminish.

Neither of these cases are about sending out a "cease and desist" order when you see your copyright being violated. But that's precisely what you must do when you see trademark being violated, because it's not the mark itself that you care about, but the association of the mark with a particular company.