Your definition for non-sequitur is correct, however the conclusion that Predators are failing to come of age is a logical conclusion of the stated premise. The actual issue, which you pointed out, is that of using a false or faulty premise (that all Predators in the movies are on their first hunts). The validity of an argument isn’t a function of how true a premise is. So you were right that op was wrong in their conclusions, you just mislabeled the issue